Cool-season annual pastures with clovers to supplement wintering beef cows nursing calves

In December of 3 years, 87 beef cows with nursing calves （.594 ± 9.8 kg; calving season, September to November） at side were stratified by body condition score, body weight, cow age, and calf gender and divided randomly into 6 groups assigned to 1 of 6 cool-season annual pastures （0.45 ha/cow） that had been interseeded into a dormant common bermudagrass （Cynodon dactylon [L.] Pers.）/bahiagrass （Paspalum notatum Flugge） sod. Pastures contained 1 of the following 3 seeding mixtures （2 pastures/mixture）： 1） wheat （Triticum aestivurn L.） and ryegrass （Lofium multiflorum Lain., WRG）, 2） wheat and ryegrass plus red clover （Trifolium pretense L, WRR）, or 3） wheat and ryegrass plus white （Trifofium repens L.） and crimson clovers （Trifolium incarnatum L., WRW）. All groups had ad libitum access to grass hay （12% crude protein; 58% total digestible nutrients）. The second week in December, cow estrous cycles were synchronized and artificially inseminated. In late December, a bull was placed with each group for 60-d. Data were analyzed with an analysis of variance using a mixed model containing treatment as the fixed effect and year as the random effect. Body weight and condition scores did not differ （P ≥ 0.27） among cows between February and June. Calf birth weights or average daily gain did not differ （P≥ 0.17） among treatments; however, calves grazing pastures with clovers did tend （P= 0.06） to weigh more than calves grazing grass only. Weaning weight per cow exposed to a bull was greater （P= 0.02） for WRR and WRW than WRG. Cows grazing winter-annual pastures containing clovers tended to wean more calf body weight per cow exposed to a bull than cows grazing the grass only pastures.

Artificial Induction of Twinning by an Active Immunization of Beef Cows Against Inhibin Partially Purified from Porcine Seminal Plasma

Two hundred and seventy multiparous Chinese Yellow cattle (beef) were selected at 1 to 3 months postpartum and divided into three groups (90 cows for each). Animals were given both a primary and booster immunizations with a total dose of 3 mg (Group Th) or 1.5 mg (Group Tl) of seminal preparation containing inhibin activity, emulsified with Freund's complete adjuvant and incomplete adjuvant (for booster) , at 3 or 4-week intervals. Other cows were treated with the same volume of seminal preparation without inhibin activity as procedures mentioned above to serve as a control (Group C). Artificial inseminations were given twice at 8 - 12 h intervals when the cow was in heat. Jugular venous blood samples were collected from each cow and used to assay the presence of antibody against seminal preparation by double-diffusion in agar precipitation test and to detect the titer of inhibin antibody by an ELISA method. Data from 247 cows showed that 83.9% (73/87) of cows were in estrus and ovulated 89 ova altogether, of which 19 cows ovulated twin ova and 15 cows produced twins in Group Th (n = 87). However, only 61.1% (44/72) of cows in Group TI (n = 72) and 62.5% (55/88) of cows in Group C were in estrus and ovulated 46 and 52 ova altogether respectively. The ovulation rate (1.27 ± 0.03), calving rate (126.3%) and twinning rate (26.3%) in Group Th were greater than those in Groups Tl or C (P<0.01). Furthermore, the ovulation rate was associated with antibody titer in sera of immunized animals (r = 0.7507, P<0.01). These results indicate that active immunization of postpartum cows against inhibin purified from porcine seminal plasma may increase the ovulation rate and induce twinning, suggesting the potential to develop a method to improve fertility in cows.