ABSTRACT
The effects of cooling and recombinant bovine somatotropin (rbST) on milk yield, reproductive performance, and health of Jersey cattle during summer thermal stress were measured for 2 yr. Cows were assigned to one of two groups based upon days in milk (DIM), parity, and genetic index. Year 1 and year 2 control cows (n = 143, n = 183, respectively) were housed in a pen with only shades. Cooled treatment cows each year (n = 142, n = 180) were housed with a spray and fan system for evaporative cooling. Cows were assigned at various days postpartum, not before d 63, coincident with commencement of rbST injections. One half of cows in each group received rbST on d 63 postpartum. Cows were assigned to the shade trial ranging from d 63 to 190. Cooled versus noncooled DIM were similar at the start of the trial. Trials began on July 1, 1999, and July 1, 2000, and concluded on September 30, 1999, and September 25, 2000. The ANOVA of daily milk weight data was conducted utilizing a 2 x 2 factorial design with cooling and rbST treatments as main effects. Cooling in combination with rbST increased milk yield compared with no cooling and no rbST for 1999 and 2000 (25.5 versus 21.8 kg/d, and 23.7 versus 20.5 kg/d, respectively). In general, cooling improved health and reproductive performance.
Subject(s)
Cattle Diseases/physiopathology , Dairying/methods , Hot Temperature , Stress, Physiological/veterinary , Animals , Cattle , Cold Temperature , Female , Growth Hormone/administration & dosage , Humidity , Lactation , Pregnancy , Reproduction , Seasons , Stress, Physiological/physiopathology , TemperatureABSTRACT
There are a number of options for hormonal management of post partum dairy cows; however, only a few studies have made direct comparisons of these programs in commercial herd settings. We compared reproductive management programs of 2 commercial dairy herds to evaluate the efficacy of prostaglandin-based treatment regimens on reproductive outcomes. Cows in Herd A were left untreated and served as the negative controls. Cows in Herd B were given PGF2alpha every 14 d until first insemination beginning 45 d post partum and served as the positive controls. Treatment 1 (Ovsynch), initiated randomly during the estrous cycle, consisted of sequential injections of GnRH, PGF2alpha, GnRH again and insemination 16 to 20 h later. Treatment 2 consisted of an Ovsynch protocol, as described above, which was begun 7 d post estrus (Ovsynch + 7). In Herd A, the number of days from parturition to conception (days open) for controls, for Ovsynch and for Ovsynch + 7 were 126, 112 and 102, respectively. In Herd B, respective days open were 102, 100 and 93 for controls, Ovsynch and Ovsynch + 7. Hormonal intervention reduced the number of days open in both herds.
