Effects of short-term nutritional increase before artificial insemination on average daily gain and reproductive efficiency in March-calving beef heifer development systems

Objective: Our objective was to evaluate increased nu- tritional energy before AI on BW, ADG, and reproductive efficiency in heifers developed on range or in a drylot. Materials and Methods: A 3-yr study used Angus crossbred heifers (n = 100/yr) near North Platte, Nebras- ka. Heifers were stratified by BW and assigned to 1 of 3 treatments. During winter development (131 ± 3.5 d/yr), heifers grazed upland range (RANGE) or were fed a drylot diet in 2 pens with a targeted gain of 0.68 kg/d to achieve 65% of mature BW (6.35 kg/head per day hay, 2.27 kg/ head per day wet corn gluten feed, and 0.34 kg/head per day supplement). Thirty-three days before AI, one dry- lot group remained on this diet (DLLO) while the other (DLHI) received an additional 4.08 kg/head per day wet corn gluten feed. Heifers developed on RANGE received 0.45 kg/head per day of a 29% CP, dried distillers grain– based pellet until 38 d before AI, when they were fed the DLLO diet. Results and Discussion: Prebreeding BW was great- er for DLHI (375 ± 3.4 kg) and DLLO (363 ± 3.4 kg) compared with RANGE (312 ± 3.4 kg), but breeding ADG was greater for RANGE (0.69 ± 0.01 kg) compared with DLHI (0.35 ± 0.02 kg) and DLLO (0.37 ± 0.02 kg). Pregnancy rates to AI were similar among DLHI (69%), DLLO (63%), and RANGE (49%); final pregnancy rates tended to be different: DLHI (96%), DLLO (95%) and RANGE (84%). Calving rate and calving in the first 21 d was similar. Implications and Applications: Greater nutrient and energy intake for DLHI and DLLO led to greater BW and ADG compared with RANGE, but short-term nutri- tional increase had no effect on pregnancy rate to AI nor final pregnancy rates

Gene Expression Profiling of Preovulatory Follicle in the Buffalo Cow: Effects of Increased IGF-I Concentration on Periovulatory Events

The preovulatory follicle in response to gonadotropin surge undergoes dramatic biochemical, and morphological changes orchestrated by expression changes in hundreds of genes. Employing well characterized bovine preovulatory follicle model, granulosa cells (GCs) and follicle wall were collected from the preovulatory follicle before, 1, 10 and 22 h post peak LH surge. Microarray analysis performed on GCs revealed that 450 and 111 genes were differentially expressed at 1 and 22 h post peak LH surge, respectively. For validation, qPCR and immunocytochemistry analyses were carried out for some of the differentially expressed genes. Expression analysis of many of these genes showed distinct expression patterns in GCs and the follicle wall. To study molecular functions and genetic networks, microarray data was analyzed using Ingenuity Pathway Analysis which revealed majority of the differentially expressed genes to cluster within processes like steroidogenesis, cell survival and cell differentiation. In the ovarian follicle, IGF-I is established to be an important regulator of the above mentioned molecular functions. Thus, further experiments were conducted to verify the effects of increased intrafollicular IGF-I levels on the expression of genes associated with the above mentioned processes. For this purpose, buffalo cows were administered with exogenous bGH to transiently increase circulating and intrafollicular concentrations of IGF-I. The results indicated that increased intrafollicular concentrations of IGF-I caused changes in expression of genes associated with steroidogenesis (StAR, SRF) and apoptosis (BCL-2, FKHR, PAWR). These results taken together suggest that onset of gonadotropin surge triggers activation of various biological pathways and that the effects of growth factors and peptides on gonadotropin actions could be examined during preovulatory follicle development

Suboptimal herd performance amplifies the spread of infectious disease in the cattle industry

Farms that purchase replacement breeding cattle are at increased risk of introducing many economically important diseases. The objectives of this analysis were to determine whether the total number of replacement breeding cattle purchased by individual farms could be reduced by improving herd performance and to quantify the effects of such reductions on the industry-level transmission dynamics of infectious cattle diseases. Detailed information on the performance and contact patterns of British cattle herds was extracted from the national cattle movement database as a case example. Approximately 69% of beef herds and 59% of dairy herds with an average of at least 20 recorded calvings per year purchased at least one replacement breeding animal. Results from zero-inflated negative binomial regression models revealed that herds with high average ages at first calving, prolonged calving intervals, abnormally high or low culling rates, and high calf mortality rates were generally more likely to be open herds and to purchase greater numbers of replacement breeding cattle. If all herds achieved the same level of performance as the top 20% of herds, the total number of replacement beef and dairy cattle purchased could be reduced by an estimated 34% and 51%, respectively. Although these purchases accounted for only 13% of between-herd contacts in the industry trade network, they were found to have a disproportionately strong influence on disease transmission dynamics. These findings suggest that targeting extension services at herds with suboptimal performance may be an effective strategy for controlling endemic cattle diseases while simultaneously improving industry productivity

Energetic-protein supplementation in the last 60 days of gestation improves performance of beef cows grazing tropical pastures

Abstract Background Nutrition is one of the most important factors that affect animal performance, and it therefore also impacts on financial results in beef systems. In this way, finding the best strategy for feeding supplements is of paramount importance. Aiming to evaluate the effect of supplement feeding strategies for beef cows in the last third of gestation, two experiments were conducted. In Experiment 1, 35 pregnant Nellore cows were assigned to a completely randomized design with four treatments: control, which received no supplement; supplementation for the last 30 d of gestation (30-d; 3.0 kg/d); supplementation for the last 60 d of gestation (60-d; 1.5 kg/d); or supplementation for the last 90 d of gestation (90-d; 1.0 kg/d). All supplemented treatments received the same total amount of supplement throughout the experiment: 90 kg (20% of crude protein). A second experiment (Experiment 2) was delineated to evaluate the effects of the amounts offered in Experiment 1 on intake and metabolism. Four multiparous pregnant Nellore cows were assigned to a 4 × 4 Latin square design, with periods of 15 d each. Results There was a linear effect of the number of days of supplementation on calving body weight (BW; P  0.10). A significant linear effect on interval from parturition to conception (P  0.10). Nitrogen excreted through urine tended to increase linearly with the level of supplementation (P < 0.10). Conclusion Providing 1.5 kg of supplement during the last 60 d of gestation improves cow performance after calving, reducing the magnitude of BW lost, and reduces the number of days from calving to re-conception in the following breeding season compared to the usually recommended period of supplementation of 90 d pre-partum