Background: Artificial insemination is a preferred breeding method for beef heifers as it advances the genetic background, produces a predictive and profitable calving season, and extends the heifer’s reproductive li...Background: Artificial insemination is a preferred breeding method for beef heifers as it advances the genetic background, produces a predictive and profitable calving season, and extends the heifer’s reproductive life span.As reproductive efficiency in heifers is key for the success of beef cattle production systems, following artificial insemination, heifers are exposed to a bull for the remainder of the breeding season. Altogether, up to 95% of heifers might become pregnant in their first breeding season. Heifers that do not become pregnant at the end of the breeding season represent an irreparable economical loss. Additionally, heifers conceiving late in the breeding season to natural service, although acceptable, poses serious losses to producers. To minimize losses due to reproductive failure, different phenotypic parameters can be assessed and utilized as selection tools. Here, we tested the hypothesis that in a group of pre-selected heifers, records of weaning weight, age at weaning, age at artificial insemination, and age of dam differ among heifers of varied reproductive outcomes during the first breeding season.Results: None of the parameters tested presented predictive ability to discriminate the heifers based on the response variable(‘pregnant to artificial insemination’, ‘pregnant to natural service’, ‘not pregnant’). Heifers categorized with body condition score = 6 and reproductive tract score ≥ 4 had the greatest proportion of pregnancy to artificial insemination(49% and 44%, respectively). Furthermore, it was notable that heifers presenting body condition score = 6 and reproductive tract score = 5 presented the greatest pregnancy rate at end of the breeding season(89%). Heifers younger than 368 d at the start of the breeding season did not become pregnant to artificial insemination. Those young heifers had 12.5% chance to become pregnant in their first breeding season,compared to 87.5% if the heifers were older than 368 days.Conclusion: Our results suggest that beef heifers with body condition score = 6 and reproductive tract score ≥ 4 are more likely to become pregnant to artificial insemination. Careful assessment should be undertaken when developing replacement heifers that will not reach 12 months of age by the beginning of the breeding season.展开更多
Background: High-altitude pulmonary hypertension(HAPH) is a life-threating condition for animals in high altitude,and disturbance of endothelial nitric oxide(NO) synthesis contributes to its pathogenesis. N-carbamylgl...Background: High-altitude pulmonary hypertension(HAPH) is a life-threating condition for animals in high altitude,and disturbance of endothelial nitric oxide(NO) synthesis contributes to its pathogenesis. N-carbamylglutamate(NCG), which enhances arginine synthesis, promotes endogenous synthesis of NO. In this study, we determined the effects of NCG on alleviating HAPH in Holstein heifers that ascended to Tibet(Lhasa, 3,658 m).Methods: Exp. 1, 2,000 Holstein heifers were transported from low elevation(1,027 m) to Lhasa. After being exposed to hypoxia for 1 yr, Holstein heifers were assigned to a healthy group(Control, n = 6) with mean pulmonary hypertension(mPAP) < 41 mmHg, and an HAPH affected group(HAPH, n = 6) with mPAP > 49 mmHg.Lung tissues were collected to evaluate histopathological changes and the expression of endothelial nitric oxide synthase(eNOS). Exp. 2, ten healthy heifers and 10 HAPH affected heifers were supplemented with NCG(20 g/d per heifer) for 4 wk. Physiological parameters were determined and blood samples were collected on d-1 and d 28 of the feeding trial.Results: Expression of e NOS in small pulmonary arteriole intima was higher in the healthy than HAPH group(P = 0.006), whereas HAPH group had significantly thicker media and adventitia than healthy group(all P < 0.05). The mRNA of eNOS and protein level of eNOS were higher in the lungs of heifers in the healthy group than in the HAPH group(both P < 0.001), whereas endothelin-1 protein levels were higher in HAPH group than in the healthy group(P = 0.025). NCG supplementation decreased mPAP and ammonia(both P = 0.001), whereas it increased the expression of eNOS, arginine, and plasma NO(all P < 0.05).Conclusions: The expression of eNOS was decreased in Holstein heifers with HAPH. NCG supplementation decreased m PAP through the restoration of eNOS and endogenous NO synthesis.展开更多
The current review is designed with aims to highlight the impact of heat stress(HS) on calves and heifers and to suggest methods for HS alleviation. HS occurs in animals when heat gain from environment and metabolism ...The current review is designed with aims to highlight the impact of heat stress(HS) on calves and heifers and to suggest methods for HS alleviation. HS occurs in animals when heat gain from environment and metabolism surpasses heat loss by radiation, convection, evaporation and conduction. Although calves and heifers are comparatively heat resistant due to less production of metabolic heat and more heat dissipation efficiency, they still suffer from HS to some degree. Dry matter intake and growth performance of calves and heifers are reduced during HS because of redistributing energy to heat regulation through a series of physiological and metabolic responses, such as elevated blood insulin and protein catabolism. Enhanced respiration rate and panting during HS accelerate the loss of CO2, resulting in altered blood acid-base chemistry and respiratory alkalosis. HS-induced alteration in rumen motility and microbiota affects the feed digestibility and rumen fermentation. Decreased luteinizing hormone, estradiol and gonadotrophins due to HS disturb the normal estrus cyclicity, depress follicular development, hence the drop in conception rate. Prenatal HS not only suppresses the embryonic development by the impaired placenta, which results in hypoxia and malnutrition, but also retards the growth, immunity and future milk production of newborn calves. Based on the above challenges, we attempted to describe the possible impacts of HS on growth, health, digestibility and reproduction of calves and heifers. Likewise, we also proposed three primary strategies for ameliorating HS consequences. Genetic development and reproductive measures, such as gene selection and embryo transfers, are more likely long-term approaches to enhance heat tolerance. While physical modification of the environment, such as shades and sprinkle systems, is the most common and easily implemented measure to alleviate HS. Additionally, nutritional management is another key approach which could help calves and heifers maintain homeostasis and prevent nutrient deficiencies because of HS.展开更多
Background: Upon binding luteinizing hormone in the ovary, the luteinizing hormone/choriogonadotropin receptor (LHCGR) is necessary for follicular maturation and ovulation, as well as luteal function. We detected m...Background: Upon binding luteinizing hormone in the ovary, the luteinizing hormone/choriogonadotropin receptor (LHCGR) is necessary for follicular maturation and ovulation, as well as luteal function. We detected mutations in the LHCGR gene and evaluated their association with superovulation. Methods: Using polymerase chain reaction-single strand sequencing, we examined polymorphisms in LHCGR and Chinese Holstein heifers. conformation polymorphism (PCR-SSCP) and DNA the genotypes associated with superovulation traits in 127 Results: A G/T polymorphism (ss52050737) in exon 11 was significantly associated with the total number of ova and the number of transferable embryos. Conclusions: LHCGR may be a new predictor for superovulation in Chinese Holstein heifers.展开更多
There are many inputs into the dairy replacement herd which impact not only on the cost of rearing heifers from birth to first calving, but also on their future longevity and production potential. This study determine...There are many inputs into the dairy replacement herd which impact not only on the cost of rearing heifers from birth to first calving, but also on their future longevity and production potential. This study determined the current cost of rearing dairy heifers in the UK through the calculation and analysis of individual costs on a subset of 102 UK dairy farms. Each farm was visited and an extensive heifer rearing questionnaire was completed. Current heifer rearing practices were recorded to provide insight into critical management decisions. A cost analysis workbook was developed to calculate the costs of inputs in the preweaning period for labour, calving, feed, housing, health treatments and vaccinations, waste storage, machinery and equipment, and utilities. The average age at weaning was 62 d. The mean cost of rearing from birth to weaning was £195.19 per heifer with a mean daily cost of £3.14 (excluding the opportunity cost of the calf). This ranged from £1.68 to £6.11 among farms, reflecting major differences in management strategies and efficiency. The highest contribution to total costs came from feed (colostrum, milk, starter and forage) at 48.5% with milk feeding making up the greatest proportion of this at 37.3%. The next major expenses were bedding and labour, contributing 12.3% and 11.2% respectively. Unsurprisingly, delaying age at weaning increased total cost by £3.53 per day. Total costs were on average 45% higher on organic farms than conventional due to higher feed costs and later weaning. Calving pattern also had a strong association with the total cost being lowest with spring calving, intermediate with autumn calving and highest in multi block and all year round calving herds.展开更多
Age at first calving (AFC) affects the profitability of dairy enterprises. This study examined the relationships between AFC and subsequent fertility, milk production and survival up to third calving in UK Holstein-Fr...Age at first calving (AFC) affects the profitability of dairy enterprises. This study examined the relationships between AFC and subsequent fertility, milk production and survival up to third calving in UK Holstein-Friesian heifers;Study 1 comprised 134 consecutively born heifers from the same herd (AFC 764 ± 8 days) and Study 2 contained 445 heifers born on 17 farms (AFC 796 ± 6 days). Growth rates and fertility during rearing were monitored and animals were subsequently divided into four AFC groups for analysis: <23 months, 23 - 25 months, 26 - 30 months and >30 months. The actual AFC reflected both growth rate and heifer fertility, with later calving heifers already lighter by 6 months of age. The proportion conceiving to first service was highest (93% and 84% for Studies 1 and 2, respectively) for the youngest AFC group. Fertility in the first lactation was best in cows calving at 23 - 25 months and worst in the oldest AFC group. Milk production parameters in the first and second lactations were broadly similar between AFC groups but significantly more heifers with an AFC < 26 months calved for a third time. These younger calving animals therefore achieved more days in milk over 5 years, with >44% of their days alive spent in milk production compared with only 18% - 40% in cows calving at ≥26 months. Hence cows with an AFC < 26 months produced the most milk in their first 5 years of life. These results indicate that an AFC of 0.75 kg/d up to 15 months and good heifer fertility and resulted in the best subsequent performance.展开更多
Dairy heifers only start to produce a return on investment at first calving. The length of the non-productive rearing period is largely governed by farmer decisions on plane of nutrition and reproduction management. P...Dairy heifers only start to produce a return on investment at first calving. The length of the non-productive rearing period is largely governed by farmer decisions on plane of nutrition and reproduction management. Primary data were collected from 101 dairy farms and a cost analysis workbook developed to calculate individual inputs in each of three periods to determine which management decisions and farm factors have the greatest influence on the total costs associated with rearing. This paper covers weaning until conception. Heifers were weaned at 62 d (range 42 - 112 d) and conceived by 509 d (range 365 - 700 d) giving an average weaning to conception period of 447 ± 60 d (range 253 to 630 d). The mean daily cost of rearing during this period was £1.65 (range £0.75 to £2.97 on different farms) giving a mean total cost of £745.94 per heifer (range £295.32 to £1745.85). This large variation was mostly due to the duration, which was mainly determined by age at first breeding (mean 476 days, range 365 - 700 d). The main contributors to total costs were feed (35.6%), labour (24.7%) and bedding (8.9%). The variables most strongly associated with the total costs were age at conception, calving pattern and breed. A multivariable model predicted an increase in mean cost of £2.26 for each extra day in age at conception. The total cost was highest in herds with all year round calving, intermediate in multi-block and lowest in spring and autumn calving herds, with Friesian x and Jersey herds having the lowest cost of rearing.展开更多
Cows (n = 21), dried off for a minimum of 45 days, and nulliparous heifers (n = 26), at ages > 18 months old, were placed on a 12-day Lactation Induction (LI) protocol. One group of animals (including both cows and...Cows (n = 21), dried off for a minimum of 45 days, and nulliparous heifers (n = 26), at ages > 18 months old, were placed on a 12-day Lactation Induction (LI) protocol. One group of animals (including both cows and heifers) received 3-minute mammary gland stimulation, along with the LI protocol. Another group, again including both cows and heifers, received no stimulation only the LI protocol This consisted of two injections of prostaglandin F2α (PGF2α;25 mg) 11 days apart, followed by subcutaneous injections of 17β-estradiol (0.1 mg/kg BW/d) and progesterone (0.25 mg/kg BW/d) beginning 1 day later and continuing for seven (7) days. After this step, all animals received another injection of PGF2α on day 8, followed by intramuscular injections of reserpine (5 mg/d) and dexamethasone (20 mg/d) on each of days 9 to 12. All animals were milked, beginning on day 13, for a period of 154 days. For all animals, the success rate for lactation induction was 78% ± 6.3% and the mean weekly milk yield was 78.2 kg. Neither value was affected by mammary stimulation. Parity did not significantly impact on the success rate but it did affect the mean weekly milk yield. Milk yield varied significantly (p < 0.001) with week, peaking during week 9. Peak milk production and persistency were 101.6 kg ± 5.9 kg and 16.9 weeks ± 2.4 weeks respectively, with neither being significantly (α = 0.05 level) affected by stimulation or by parity. However, heifers (at 8.2 weeks ± 1.0 week) tended (p = 0.1) to reach peak milk production earlier than cows (at 10.7 weeks ± 1.3). The milk produced was sold at a net profit per animal treated of $2206.31 TT. Hence, one can conclude that a Lactation Induction protocol can be a useful management tool to increase production and profitability of dairy operations in the tropics.展开更多
Good management of the pregnant heifer is crucial to ensure that she is well grown and healthy and calves down easily before joining the milking herd. This study collected primary data on all aspects of heifer managem...Good management of the pregnant heifer is crucial to ensure that she is well grown and healthy and calves down easily before joining the milking herd. This study collected primary data on all aspects of heifer management on 101 UK farms during heifer pregnancy from conception to calving including farm factors and associated costs of system inputs. A cost analysis workbook was developed to calculate the cost of rearing per heifer for each of the study farms. Associations between cost of rearing and farms factors were determined using linear regression and analysis of variance. Heifers had a mean age of conception of 509 d (range 365 - 700 d) and an age at first calving of 784 d (range 639 - 973 d). The mean total cost of rearing during pregnancy was £450.36 (range £153.11 to £784.00) with a mean daily cost of £1.64 (range £0.56 to £2.86). The inputs contributing the most to cost were feed (32.7%), labour (23.8%) and slurry disposal (11.2%). Total purchased and homegrown feed and grazing contributed between 25.5% and 65.4% of total costs with a mean contribution of 43.6%. The cost of rearing was lowest in spring calving herds and highest in all year round calving herds with intermediate values in autumn and multi block calving herds. The main variables influencing the cost were the number of days spent at grass, age at first calving, calving pattern, breed, herd size and region. Each extra day in age at first calving increased the mean cost of rearing during pregnancy by £0.33/d whereas every extra day at grass reduced the cost by £1.75/d.展开更多
Heifers grazing winter range require supplemental nutrients to complement dormant forage to achieve optimal growth and performance. A study was conducted to evaluate nutritional environment and effect of different sup...Heifers grazing winter range require supplemental nutrients to complement dormant forage to achieve optimal growth and performance. A study was conducted to evaluate nutritional environment and effect of different supplementation strategies for developing heifers grazing dormant winter range. Eighty-four Angus crossbred heifers were stratified by body weight at weaning, allocated to one of six replicated pastures, and randomly assigned one of three supplemental treatments: 1) 908 g/d of a control supplement providing 340 g·hd-1·d-1 of CP with 130 g of rumen undegradable protein (RUP) and 614 MJ of ME (LRUP);2) 908 g/d of a RUP supplement providing 340 g·hd-1·d-1 of CP with 170 g of RUP and 567 MJ of ME (HRUP);or 3) 1814 g/d of a protein and energy supplement providing 340 g·hd-1·d-1 of CP with 120 g of RUP + 100 g of propionate salt (NutroCalTM, Kemin Industries, Inc.) and 1222 MJ of ME (LRUP + E). Body weights were taken in November, with monthly 12 h shrunk BW from January thru April, and again in September (at time of pregnancy diagnosis). Heifer average daily gain was similar throughout the developmental period except from d125 to d159 where LRUP + E supplemented heifers had greater gains展开更多
The objectives of this study were to evaluate the effect of using multiple dietary inclusion rates of alkaline aqueous lignin by-product(AALB),in replacing a commercial binder,on the preference and feeding behavior of...The objectives of this study were to evaluate the effect of using multiple dietary inclusion rates of alkaline aqueous lignin by-product(AALB),in replacing a commercial binder,on the preference and feeding behavior of dairy heifers,and in vitro digestibility.In the experiment I,five pelleted diets including negative control(no-binder),commercial lignosulfonate binder,and 1.6%,3.2%,and 4.8%of AALB were tested.In the experiment II,five pelleted diets including negative control,positive control(2%molasses),and 1%,2.4%,and 3.8%of AALB(all combined with 2%of molasses)were tested.Feeding behavior and preference were determined for 60 min per animal per evaluation.In vitro digestibility was determined for each pelleted diet for 48 h over five incubation runs.Results from Experiment I showed animals receiving 1.6%of AALB diet showed the greatest preference(dry matter(DM),intake)and a greater number of approaches with eating than other diets.The preference was lower when animals received control or 4.8%AALB diets relative to other diets.Results from Experiment II revealed animals receiving 3.8%AALB combined with molasses showed the greatest DM intake preference over 60 min,and DM intake per approach.Diets that included 2.4%and 3.8%of AALB combined with molasses presented the greatest in vitro DM digestibility.Overall,heifers showed a greater intake when receiving pelleted diets with 1.6%AALB.Furthermore,preference,intake over 60 min,and in vitro DM digestibility,were greater in the pelleted diets that contained higher rates of AALB when combined with molasses.展开更多
40 in-calf heifers were observed to examine the effect of timbers placing in passage area on their use of cubicle beds. Prior to the experiment preliminary observation was taken on these 40 heifers and they were divid...40 in-calf heifers were observed to examine the effect of timbers placing in passage area on their use of cubicle beds. Prior to the experiment preliminary observation was taken on these 40 heifers and they were divided into two even groups (cubicle user(or control) group versus cubicle refusal (or experimental) group by whether they properly used the cubicle beds or not. The timbers were placed in passage and feeding areas for the cubicle refusal group to force the animls to lie in the cubicle beds. The results of this experiment showed that feeding behaviour was unaffected by the presence of the timbers, but lying acitvity was about 8% higher for the experimental group, which led to a mean of almost 2 hours longer lying time over 24 h. After the timbers were removed, there was a significant decline in lying by the experimental group. The diurnal pattern of lying behaviour in cubicles indicated that the major effect on lying activity exerted by the presence of the timbers was seen during midnight to 10:00 am. Also during this times, the experimental group in the pres-ence of the timbers tended to show more lying in cubicles than control group. At the end of the experiment, 95% of the heifers were found to be correctly using the cubicle beds, and on the negative side three heifers developed a slight injury on their legs or hocks caused by the timber.展开更多
The objective of this experiment was to evaluate the effect of supplementing rumen-protected Lys based on a Lys-deficient diet on liver metabolism in growing Holstein heifers.The experiment was conducted for 3 months ...The objective of this experiment was to evaluate the effect of supplementing rumen-protected Lys based on a Lys-deficient diet on liver metabolism in growing Holstein heifers.The experiment was conducted for 3 months with 36 Holstein heifers(initial body weight:200±9.0 kg;7-month-old).Heifers were randomly assigned to 2 diets based on corn,soybean meal,alfalfa hay,and wheat bran:control,Lysdeficient diet(LD;0.66%Lys in diet),and Lys-adequate diet(LA;1.00%Lys in diet).The results showed no difference in growth performance between the 2 groups(P>0.05).However,there was a clear trend of increasing feed conversion rate with Lys supplementation(0.05<P<0.01).The serum urea nitrogen concentration was significantly decreased,and the aspartate aminotransferase-to-alanine aminotransferase ratio was significantly decreased by Lys supplementation(P<0.05).Moreover,growing heifers fed a Lys-adequate diet had lower levels of urine nitrogen excretion and higher levels of the biological value of nitrogen(P<0.05).Metabolomic analysis revealed that 5 types of phosphatidylcholine and 3 types of ceramide were significantly increased and enriched in sphingolipid metabolism and glycero phospholipid metabolism(P<0.05).His,Leu,and Asp levels were significantly decreased in the liver following Lys supplementation(P<0.05).In conclusion,Lys supplementation may promote the synthesis of body tissue proteins,as evidenced by significantly decreased amino acids in the liver and urine N excretion,it also improves hepatic lipid metabolism by providing lipoprotein precursors.展开更多
基金partially funded by the Alabama Agricultural Experiment Stationthe Hatch program of the National Institute of Food and Agriculture,U.S.Department of Agriculture
文摘Background: Artificial insemination is a preferred breeding method for beef heifers as it advances the genetic background, produces a predictive and profitable calving season, and extends the heifer’s reproductive life span.As reproductive efficiency in heifers is key for the success of beef cattle production systems, following artificial insemination, heifers are exposed to a bull for the remainder of the breeding season. Altogether, up to 95% of heifers might become pregnant in their first breeding season. Heifers that do not become pregnant at the end of the breeding season represent an irreparable economical loss. Additionally, heifers conceiving late in the breeding season to natural service, although acceptable, poses serious losses to producers. To minimize losses due to reproductive failure, different phenotypic parameters can be assessed and utilized as selection tools. Here, we tested the hypothesis that in a group of pre-selected heifers, records of weaning weight, age at weaning, age at artificial insemination, and age of dam differ among heifers of varied reproductive outcomes during the first breeding season.Results: None of the parameters tested presented predictive ability to discriminate the heifers based on the response variable(‘pregnant to artificial insemination’, ‘pregnant to natural service’, ‘not pregnant’). Heifers categorized with body condition score = 6 and reproductive tract score ≥ 4 had the greatest proportion of pregnancy to artificial insemination(49% and 44%, respectively). Furthermore, it was notable that heifers presenting body condition score = 6 and reproductive tract score = 5 presented the greatest pregnancy rate at end of the breeding season(89%). Heifers younger than 368 d at the start of the breeding season did not become pregnant to artificial insemination. Those young heifers had 12.5% chance to become pregnant in their first breeding season,compared to 87.5% if the heifers were older than 368 days.Conclusion: Our results suggest that beef heifers with body condition score = 6 and reproductive tract score ≥ 4 are more likely to become pregnant to artificial insemination. Careful assessment should be undertaken when developing replacement heifers that will not reach 12 months of age by the beginning of the breeding season.
基金provided by the National Dairy Industry and Technology System(Beijing,P.R.China)
文摘Background: High-altitude pulmonary hypertension(HAPH) is a life-threating condition for animals in high altitude,and disturbance of endothelial nitric oxide(NO) synthesis contributes to its pathogenesis. N-carbamylglutamate(NCG), which enhances arginine synthesis, promotes endogenous synthesis of NO. In this study, we determined the effects of NCG on alleviating HAPH in Holstein heifers that ascended to Tibet(Lhasa, 3,658 m).Methods: Exp. 1, 2,000 Holstein heifers were transported from low elevation(1,027 m) to Lhasa. After being exposed to hypoxia for 1 yr, Holstein heifers were assigned to a healthy group(Control, n = 6) with mean pulmonary hypertension(mPAP) < 41 mmHg, and an HAPH affected group(HAPH, n = 6) with mPAP > 49 mmHg.Lung tissues were collected to evaluate histopathological changes and the expression of endothelial nitric oxide synthase(eNOS). Exp. 2, ten healthy heifers and 10 HAPH affected heifers were supplemented with NCG(20 g/d per heifer) for 4 wk. Physiological parameters were determined and blood samples were collected on d-1 and d 28 of the feeding trial.Results: Expression of e NOS in small pulmonary arteriole intima was higher in the healthy than HAPH group(P = 0.006), whereas HAPH group had significantly thicker media and adventitia than healthy group(all P < 0.05). The mRNA of eNOS and protein level of eNOS were higher in the lungs of heifers in the healthy group than in the HAPH group(both P < 0.001), whereas endothelin-1 protein levels were higher in HAPH group than in the healthy group(P = 0.025). NCG supplementation decreased mPAP and ammonia(both P = 0.001), whereas it increased the expression of eNOS, arginine, and plasma NO(all P < 0.05).Conclusions: The expression of eNOS was decreased in Holstein heifers with HAPH. NCG supplementation decreased m PAP through the restoration of eNOS and endogenous NO synthesis.
基金funded by National Key Research and Development Program of China (2018YFD0501600)Key Research and Development Project of Hebei (19226625D)。
文摘The current review is designed with aims to highlight the impact of heat stress(HS) on calves and heifers and to suggest methods for HS alleviation. HS occurs in animals when heat gain from environment and metabolism surpasses heat loss by radiation, convection, evaporation and conduction. Although calves and heifers are comparatively heat resistant due to less production of metabolic heat and more heat dissipation efficiency, they still suffer from HS to some degree. Dry matter intake and growth performance of calves and heifers are reduced during HS because of redistributing energy to heat regulation through a series of physiological and metabolic responses, such as elevated blood insulin and protein catabolism. Enhanced respiration rate and panting during HS accelerate the loss of CO2, resulting in altered blood acid-base chemistry and respiratory alkalosis. HS-induced alteration in rumen motility and microbiota affects the feed digestibility and rumen fermentation. Decreased luteinizing hormone, estradiol and gonadotrophins due to HS disturb the normal estrus cyclicity, depress follicular development, hence the drop in conception rate. Prenatal HS not only suppresses the embryonic development by the impaired placenta, which results in hypoxia and malnutrition, but also retards the growth, immunity and future milk production of newborn calves. Based on the above challenges, we attempted to describe the possible impacts of HS on growth, health, digestibility and reproduction of calves and heifers. Likewise, we also proposed three primary strategies for ameliorating HS consequences. Genetic development and reproductive measures, such as gene selection and embryo transfers, are more likely long-term approaches to enhance heat tolerance. While physical modification of the environment, such as shades and sprinkle systems, is the most common and easily implemented measure to alleviate HS. Additionally, nutritional management is another key approach which could help calves and heifers maintain homeostasis and prevent nutrient deficiencies because of HS.
基金supported by grant #2011BAD19B01,#2011BAD19B03 and #2011BAD19B04 from the National Key Technology R&D program#2011AA100303 from National High-Tech R&D Program
文摘Background: Upon binding luteinizing hormone in the ovary, the luteinizing hormone/choriogonadotropin receptor (LHCGR) is necessary for follicular maturation and ovulation, as well as luteal function. We detected mutations in the LHCGR gene and evaluated their association with superovulation. Methods: Using polymerase chain reaction-single strand sequencing, we examined polymorphisms in LHCGR and Chinese Holstein heifers. conformation polymorphism (PCR-SSCP) and DNA the genotypes associated with superovulation traits in 127 Results: A G/T polymorphism (ss52050737) in exon 11 was significantly associated with the total number of ova and the number of transferable embryos. Conclusions: LHCGR may be a new predictor for superovulation in Chinese Holstein heifers.
文摘There are many inputs into the dairy replacement herd which impact not only on the cost of rearing heifers from birth to first calving, but also on their future longevity and production potential. This study determined the current cost of rearing dairy heifers in the UK through the calculation and analysis of individual costs on a subset of 102 UK dairy farms. Each farm was visited and an extensive heifer rearing questionnaire was completed. Current heifer rearing practices were recorded to provide insight into critical management decisions. A cost analysis workbook was developed to calculate the costs of inputs in the preweaning period for labour, calving, feed, housing, health treatments and vaccinations, waste storage, machinery and equipment, and utilities. The average age at weaning was 62 d. The mean cost of rearing from birth to weaning was £195.19 per heifer with a mean daily cost of £3.14 (excluding the opportunity cost of the calf). This ranged from £1.68 to £6.11 among farms, reflecting major differences in management strategies and efficiency. The highest contribution to total costs came from feed (colostrum, milk, starter and forage) at 48.5% with milk feeding making up the greatest proportion of this at 37.3%. The next major expenses were bedding and labour, contributing 12.3% and 11.2% respectively. Unsurprisingly, delaying age at weaning increased total cost by £3.53 per day. Total costs were on average 45% higher on organic farms than conventional due to higher feed costs and later weaning. Calving pattern also had a strong association with the total cost being lowest with spring calving, intermediate with autumn calving and highest in multi block and all year round calving herds.
文摘Age at first calving (AFC) affects the profitability of dairy enterprises. This study examined the relationships between AFC and subsequent fertility, milk production and survival up to third calving in UK Holstein-Friesian heifers;Study 1 comprised 134 consecutively born heifers from the same herd (AFC 764 ± 8 days) and Study 2 contained 445 heifers born on 17 farms (AFC 796 ± 6 days). Growth rates and fertility during rearing were monitored and animals were subsequently divided into four AFC groups for analysis: <23 months, 23 - 25 months, 26 - 30 months and >30 months. The actual AFC reflected both growth rate and heifer fertility, with later calving heifers already lighter by 6 months of age. The proportion conceiving to first service was highest (93% and 84% for Studies 1 and 2, respectively) for the youngest AFC group. Fertility in the first lactation was best in cows calving at 23 - 25 months and worst in the oldest AFC group. Milk production parameters in the first and second lactations were broadly similar between AFC groups but significantly more heifers with an AFC < 26 months calved for a third time. These younger calving animals therefore achieved more days in milk over 5 years, with >44% of their days alive spent in milk production compared with only 18% - 40% in cows calving at ≥26 months. Hence cows with an AFC < 26 months produced the most milk in their first 5 years of life. These results indicate that an AFC of 0.75 kg/d up to 15 months and good heifer fertility and resulted in the best subsequent performance.
文摘Dairy heifers only start to produce a return on investment at first calving. The length of the non-productive rearing period is largely governed by farmer decisions on plane of nutrition and reproduction management. Primary data were collected from 101 dairy farms and a cost analysis workbook developed to calculate individual inputs in each of three periods to determine which management decisions and farm factors have the greatest influence on the total costs associated with rearing. This paper covers weaning until conception. Heifers were weaned at 62 d (range 42 - 112 d) and conceived by 509 d (range 365 - 700 d) giving an average weaning to conception period of 447 ± 60 d (range 253 to 630 d). The mean daily cost of rearing during this period was £1.65 (range £0.75 to £2.97 on different farms) giving a mean total cost of £745.94 per heifer (range £295.32 to £1745.85). This large variation was mostly due to the duration, which was mainly determined by age at first breeding (mean 476 days, range 365 - 700 d). The main contributors to total costs were feed (35.6%), labour (24.7%) and bedding (8.9%). The variables most strongly associated with the total costs were age at conception, calving pattern and breed. A multivariable model predicted an increase in mean cost of £2.26 for each extra day in age at conception. The total cost was highest in herds with all year round calving, intermediate in multi-block and lowest in spring and autumn calving herds, with Friesian x and Jersey herds having the lowest cost of rearing.
文摘Cows (n = 21), dried off for a minimum of 45 days, and nulliparous heifers (n = 26), at ages > 18 months old, were placed on a 12-day Lactation Induction (LI) protocol. One group of animals (including both cows and heifers) received 3-minute mammary gland stimulation, along with the LI protocol. Another group, again including both cows and heifers, received no stimulation only the LI protocol This consisted of two injections of prostaglandin F2α (PGF2α;25 mg) 11 days apart, followed by subcutaneous injections of 17β-estradiol (0.1 mg/kg BW/d) and progesterone (0.25 mg/kg BW/d) beginning 1 day later and continuing for seven (7) days. After this step, all animals received another injection of PGF2α on day 8, followed by intramuscular injections of reserpine (5 mg/d) and dexamethasone (20 mg/d) on each of days 9 to 12. All animals were milked, beginning on day 13, for a period of 154 days. For all animals, the success rate for lactation induction was 78% ± 6.3% and the mean weekly milk yield was 78.2 kg. Neither value was affected by mammary stimulation. Parity did not significantly impact on the success rate but it did affect the mean weekly milk yield. Milk yield varied significantly (p < 0.001) with week, peaking during week 9. Peak milk production and persistency were 101.6 kg ± 5.9 kg and 16.9 weeks ± 2.4 weeks respectively, with neither being significantly (α = 0.05 level) affected by stimulation or by parity. However, heifers (at 8.2 weeks ± 1.0 week) tended (p = 0.1) to reach peak milk production earlier than cows (at 10.7 weeks ± 1.3). The milk produced was sold at a net profit per animal treated of $2206.31 TT. Hence, one can conclude that a Lactation Induction protocol can be a useful management tool to increase production and profitability of dairy operations in the tropics.
文摘Good management of the pregnant heifer is crucial to ensure that she is well grown and healthy and calves down easily before joining the milking herd. This study collected primary data on all aspects of heifer management on 101 UK farms during heifer pregnancy from conception to calving including farm factors and associated costs of system inputs. A cost analysis workbook was developed to calculate the cost of rearing per heifer for each of the study farms. Associations between cost of rearing and farms factors were determined using linear regression and analysis of variance. Heifers had a mean age of conception of 509 d (range 365 - 700 d) and an age at first calving of 784 d (range 639 - 973 d). The mean total cost of rearing during pregnancy was £450.36 (range £153.11 to £784.00) with a mean daily cost of £1.64 (range £0.56 to £2.86). The inputs contributing the most to cost were feed (32.7%), labour (23.8%) and slurry disposal (11.2%). Total purchased and homegrown feed and grazing contributed between 25.5% and 65.4% of total costs with a mean contribution of 43.6%. The cost of rearing was lowest in spring calving herds and highest in all year round calving herds with intermediate values in autumn and multi block calving herds. The main variables influencing the cost were the number of days spent at grass, age at first calving, calving pattern, breed, herd size and region. Each extra day in age at first calving increased the mean cost of rearing during pregnancy by £0.33/d whereas every extra day at grass reduced the cost by £1.75/d.
文摘Heifers grazing winter range require supplemental nutrients to complement dormant forage to achieve optimal growth and performance. A study was conducted to evaluate nutritional environment and effect of different supplementation strategies for developing heifers grazing dormant winter range. Eighty-four Angus crossbred heifers were stratified by body weight at weaning, allocated to one of six replicated pastures, and randomly assigned one of three supplemental treatments: 1) 908 g/d of a control supplement providing 340 g·hd-1·d-1 of CP with 130 g of rumen undegradable protein (RUP) and 614 MJ of ME (LRUP);2) 908 g/d of a RUP supplement providing 340 g·hd-1·d-1 of CP with 170 g of RUP and 567 MJ of ME (HRUP);or 3) 1814 g/d of a protein and energy supplement providing 340 g·hd-1·d-1 of CP with 120 g of RUP + 100 g of propionate salt (NutroCalTM, Kemin Industries, Inc.) and 1222 MJ of ME (LRUP + E). Body weights were taken in November, with monthly 12 h shrunk BW from January thru April, and again in September (at time of pregnancy diagnosis). Heifer average daily gain was similar throughout the developmental period except from d125 to d159 where LRUP + E supplemented heifers had greater gains
文摘The objectives of this study were to evaluate the effect of using multiple dietary inclusion rates of alkaline aqueous lignin by-product(AALB),in replacing a commercial binder,on the preference and feeding behavior of dairy heifers,and in vitro digestibility.In the experiment I,five pelleted diets including negative control(no-binder),commercial lignosulfonate binder,and 1.6%,3.2%,and 4.8%of AALB were tested.In the experiment II,five pelleted diets including negative control,positive control(2%molasses),and 1%,2.4%,and 3.8%of AALB(all combined with 2%of molasses)were tested.Feeding behavior and preference were determined for 60 min per animal per evaluation.In vitro digestibility was determined for each pelleted diet for 48 h over five incubation runs.Results from Experiment I showed animals receiving 1.6%of AALB diet showed the greatest preference(dry matter(DM),intake)and a greater number of approaches with eating than other diets.The preference was lower when animals received control or 4.8%AALB diets relative to other diets.Results from Experiment II revealed animals receiving 3.8%AALB combined with molasses showed the greatest DM intake preference over 60 min,and DM intake per approach.Diets that included 2.4%and 3.8%of AALB combined with molasses presented the greatest in vitro DM digestibility.Overall,heifers showed a greater intake when receiving pelleted diets with 1.6%AALB.Furthermore,preference,intake over 60 min,and in vitro DM digestibility,were greater in the pelleted diets that contained higher rates of AALB when combined with molasses.
文摘40 in-calf heifers were observed to examine the effect of timbers placing in passage area on their use of cubicle beds. Prior to the experiment preliminary observation was taken on these 40 heifers and they were divided into two even groups (cubicle user(or control) group versus cubicle refusal (or experimental) group by whether they properly used the cubicle beds or not. The timbers were placed in passage and feeding areas for the cubicle refusal group to force the animls to lie in the cubicle beds. The results of this experiment showed that feeding behaviour was unaffected by the presence of the timbers, but lying acitvity was about 8% higher for the experimental group, which led to a mean of almost 2 hours longer lying time over 24 h. After the timbers were removed, there was a significant decline in lying by the experimental group. The diurnal pattern of lying behaviour in cubicles indicated that the major effect on lying activity exerted by the presence of the timbers was seen during midnight to 10:00 am. Also during this times, the experimental group in the pres-ence of the timbers tended to show more lying in cubicles than control group. At the end of the experiment, 95% of the heifers were found to be correctly using the cubicle beds, and on the negative side three heifers developed a slight injury on their legs or hocks caused by the timber.
基金funded by the Department for Environment Food & Rural Affairsthe Scottish Government+2 种基金the Department of Agriculture and Rural Development for Northern Irelandthe Welsh Government as part of the UK’s Agricultural GHG Research Platform initiative
基金supported,in part,by the Key Research and Development Program of Hebei Province(19226621D)Earmarked Fund for Beijing Dairy Industry Innovation Consortium of Agriculture Research System,Chinese Academy of Agricultural Science and Technology Innovation Project(CAAS-XTCX-2016011-01)+2 种基金Fundamental Research Funds for Central Non-profit Scientific Institution(Y2019CG08)Agricultural Science and Technology Innovation Program(CAAS-ASTIP-2017-FRI-04)Science and Technology Open Cooperation Project of Henan Province(182106000035)Study on the Pattern of Diet Amino Acid for Different Physiological Stages of Heifers。
文摘The objective of this experiment was to evaluate the effect of supplementing rumen-protected Lys based on a Lys-deficient diet on liver metabolism in growing Holstein heifers.The experiment was conducted for 3 months with 36 Holstein heifers(initial body weight:200±9.0 kg;7-month-old).Heifers were randomly assigned to 2 diets based on corn,soybean meal,alfalfa hay,and wheat bran:control,Lysdeficient diet(LD;0.66%Lys in diet),and Lys-adequate diet(LA;1.00%Lys in diet).The results showed no difference in growth performance between the 2 groups(P>0.05).However,there was a clear trend of increasing feed conversion rate with Lys supplementation(0.05<P<0.01).The serum urea nitrogen concentration was significantly decreased,and the aspartate aminotransferase-to-alanine aminotransferase ratio was significantly decreased by Lys supplementation(P<0.05).Moreover,growing heifers fed a Lys-adequate diet had lower levels of urine nitrogen excretion and higher levels of the biological value of nitrogen(P<0.05).Metabolomic analysis revealed that 5 types of phosphatidylcholine and 3 types of ceramide were significantly increased and enriched in sphingolipid metabolism and glycero phospholipid metabolism(P<0.05).His,Leu,and Asp levels were significantly decreased in the liver following Lys supplementation(P<0.05).In conclusion,Lys supplementation may promote the synthesis of body tissue proteins,as evidenced by significantly decreased amino acids in the liver and urine N excretion,it also improves hepatic lipid metabolism by providing lipoprotein precursors.