The effect of dairy heifer pre-breeding growth rate on first lactation milk yield in spring-calving, pasture-based herds.

Optimising heifer growth rate may offer an opportunity to improve lifetime milk yield per cow, enhancing the environmental and economic efficiency of dairy farming operations. The effect of dairy heifer pre-breeding average daily weight gain (ADGPB) on first lactation milk yield was investigated. This observational study employed a data set comprising 265 Holstein-Friesian, or Holstein-Friesian-cross-Jersey heifers from seven commercial, spring-calving, pasture-based dairy herds, where the major component of the diet was grazed grass. These were weighed at birth and prior to breeding and ADGPB was calculated. Milk recordings were performed throughout the heifers' first lactation and 305-day yield figures calculated from these records. Yields were corrected to 4% fat and 3.1% protein to create standardised 305-day milk yield (SMY), which was the outcome of interest. Median ADGPB was 0.72 kg/day. Median 305-day yield was 5 967 kg. Linear regression was used to investigate the effect of weight and genetic, age and first calving factors on SMY. Pre-breeding average daily weight gain, age at first calving and predicted transmitting abilities for milk protein production and calving interval were all significant in the final model, which also included the random effects of farm and month of calving within year. ADGPB was quadratically related to first lactation SMY, with an ADGPB of 0.82 kg/day corresponding to the maximum predicted SMY. The model predicted that a heifer growing at 0.82 kg/day would produce 1 120 kg more SMY than a heifer growing at 0.55 kg/day, 218 kg more than a heifer growing at 0.7 kg/day and 103 kg more than a heifer growing at 0.90 kg/day. Manipulation of heifer growth rate may offer a viable method of increasing first lactation milk yield.

The influence of short-term selenitetriglycerides supplementation on blood selenium, and hepatic, renal, metabolic and hematological parameters in dairy cows.

Selenium deficiency is a common nutritional disorder in dairy cattle globally. However, selenium supplementation can lead to selenium toxicity. This study evaluated a novel, low-toxicity selenium supplement, selenitetriglycerides, to determine its efficacy and safety in dairy cows. The study was conducted on 12 Holstein Friesian cows divided in two equal groups (control group without supplementation of selenium and experimental group with supplementation of selenitetriglycerides). Experimental cows (n=6) were orally administered 300 mg/cow/day of selenitetriglycerides for 14 days (days 1-14) and then monitored for a further 14 days (days 15-28). Blood from both groups of cows was sampled for determination of selenium concentrations, activity of aspartate aminotransferase, creatine kinase, lactate dehydrogenase, gamma- -glutamyl transferase, concentrations of triglycerides, cholesterol, non-esterified fatty acids, glucose, total protein, urea, creatinine and hematological parameters. Serum selenium concentrations in the experimental group increased significantly on day 2 (from 64.92±6.89 µg/L to 127.95±13.75 µg/L), peaked on day 7 (266.22±14.21 µg/L) and remained significantly above the initial baseline values (day 1) for 28 days. Serum selenium concentrations in the control group did not change significantly during the 28 day period (65.22 µg/L on 1st day and 64,35 µg/L on 28th day) and were significantly lower than those in the experimental group from day 2 to day 28. The results of clinical examinations, analyses of hematological parameters, and liver and kidney function tests showed that selenitetriglycerides had no adverse effect on the health or on the metabolic or haematological statuses of the cows. These findings indicate that selenitetriglycerides are safe and effective selenium supplements for cattle.

Functional characterization of SIM1-associated enhancers.

Haploinsufficiency of the single-minded homology 1 (SIM1) gene in humans and mice leads to severe obesity, suggesting that altered expression of SIM1, by way of regulatory elements such as enhancers, could predispose individuals to obesity. Here, we identified transcriptional enhancers that could regulate SIM1, using comparative genomics coupled with zebrafish and mouse transgenic enhancer assays. Owing to the dual role of Sim1 in hypothalamic development and in adult energy homeostasis, the enhancer activity of these sequences was annotated from embryonic to adult age. Of the seventeen tested sequences, two SIM1 candidate enhancers (SCE2 and SCE8) were found to have brain-enhancer activity in zebrafish. Both SCE2 and SCE8 also exhibited embryonic brain-enhancer expression in mice, and time course analysis of SCE2 activity showed overlapping expression with Sim1 from embryonic to adult age, notably in the hypothalamus in adult mice. Using a deletion series, we identified the critical region in SCE2 that is needed for enhancer activity in the developing brain. Sequencing this region in obese and lean cohorts revealed a higher prevalence of single nucleotide polymorphisms (SNPs) that were unique to obese individuals, with one variant reducing developmental-enhancer activity in zebrafish. In summary, we have characterized two brain enhancers in the SIM1 locus and identified a set of obesity-specific SNPs within one of them, which may predispose individuals to obesity.

Effect of offering rumen-protected fat supplements on fertility and performance in spring-calving Holstein-Friesian cows.

The objective of this study was to evaluate the effect of two different rumen-protected fat supplements, on reproductive performance and milk production, in grass-based spring calving cows. Two hundred and one Holstein-Friesian cows with an average lactation number of 3.6 (20% first lactation, 16% second lactation and 64% third lactation or greater) were grouped into blocks of three on the basis of calving date, lactation number and previous lactation milk yield for cows of second lactation or greater and on the basis of calving date for first lactation animals. From within-blocks individual animals were assigned at random, within 10 days post-calving, to one of the following three treatments: (1) Megalac Plus 3% (MP; 0.4kg/day, containing Ca salt of palm fatty acids and Ca salt of methionine hydroxy analogue), (2) Megapro Gold (MPG; 1.5kg/day, containing Ca salt of palm fatty acids, extracted rapeseed meal and whey permeate), and (3) Control (C; unsupplemented). Cows were supplemented for on average 103 days (range 54-134 days). The average milk yield over the first 12 weeks of lactation was higher (P<0.05) for both fat supplements compared to C and was higher for MP compared to C over the full lactation. Both supplements reduced (P<0.05) milk protein concentration over the first 6 weeks of lactation. MPG increased (P<0.05) conception rate to first service compared to C. Conception rate to first service was similar (P=0.14) on MP compared to C. For pregnancy to second service, C had a higher (P<0.05) conception rate than MP. There were no significant differences between treatments in overall pregnancy rate, services per conception, number of cows served in the first 3 weeks of the breeding season or the 6-weeks in-calf rate. Comparing the combined fat treatments to C resulted in a higher (P<0.05) conception rate to first service for the fat treatments but no significant difference in overall pregnancy rate. In conclusion, fat supplements increased conception rate to first service but did not significantly affect the proportion of cows pregnant at the end of the breeding season.

Effects of calcium salts of fatty acids and calcium salt of methionine hydroxy analogue on plasma prostaglandin F2alpha metabolite and milk fatty acid profiles in late lactation Holstein-Friesian cows.

Effects of a dietary lipid supplement containing calcium salts of fatty acids and methionine hydroxy analogue on plasma prostaglandin F2alpha (PGF2alpha) metabolite (PGFM) and milk fatty acid profiles were examined in 40 late lactation, nonpregnant, Holstein-Friesian cows for a period of 70 days. Effects on milk production, milk composition, and blood metabolites were also examined. Cows were paired on the basis of lactation number (first lactation, n = 8; second lactation, n = 32) and randomly assigned from within pairs to one of two dietary treatments: unsupplemented control (C) or 400 g per cow per day of the lipid supplement (S). Cows receiving the supplement had higher (P < 0.05) total milk production, total fat production (kg), and total lactose production (kg). Plasma cholesterol was significantly higher (P < 0.01) after 30 days of treatment in cows receiving the supplement. Cows receiving the supplement had lower (P < 0.01) concentrations of short chain milk fatty acids (C4:0 to C14:1) and higher concentrations of long chain fatty acids (C18:1 and C18:2; P < 0.01) than control animals. Oxytocin-induced prostaglandin release on Day 16 postovulation was increased (P < 0.01) in cows receiving the supplement. In conclusion, supplementation with calcium salts of fatty acids and methionine hydroxy analogue significantly increased milk yield and plasma PGFM.

Effect of a whey protein concentrate used as a colostrum substitute or supplement on calf immunity, weight gain, and health.

The efficacy of a whey protein concentrate was evaluated as a colostrum substitute or supplement in two experiments using four groups of 29 calves. In Experiment 1, calves were fed either 2 L of pooled colostrum (group 1) or 500 g of whey protein concentrate (group 2). A mean total of 123.6 and 17.7 g of Ig was fed to calves in groups 1 and 2, respectively. Mean serum IgG, total protein, and globulin concentrations and Ig antibody activities to Escherichia coli K99 and rotavirus were significantly higher for calves in group 1 at 24 to 36 h and at 3 wk of age. Weight gain from birth to 3 wk of age was significantly lower for calves in group 2. The incidence of diarrhea was high but not different between treatments. The mortality rate (0 to 3 wk) was significantly higher for calves in group 2 (27.6%) than for calves in group 1 (3.4%). In Experiment 2, calves were fed either 2 L of pooled colostrum (group 3) or a solution of 1 L of pooled colostrum plus 500 g of whey protein concentrate (group 4). A mean total of 117.2 and 69.1 g of Ig was fed to calves in groups 3 and 4, respectively. Absorption rate of IgG was significantly lower for calves in group 4. Mean serum IgG, total protein, and globulin concentrations and Ig antibody activities to E. coli K99 and rotavirus were significantly higher for calves in group 3 at 24 to 36 h and at 3 wk of age. Mortality rate, BW gain, and incidence of diarrhea did not differ significantly between groups.

Effect of feeding a mineral-vitamin supplement before calving on the calving performance of a trace element deficient dairy herd.

A split-herd, randomised mineral-vitamin supplementation experiment was carried out in a large, trace element deficient dairy herd over two years. Ten weeks before the herd's mean calving date, 147 Holstein-Friesian cows were fed grass silage on to which 50 g per head of a mineral-vitamin supplement (3000 mg copper, 500 mg iodine, 45 mg selenium and 80 mg cobalt per kg of supplement as specified) was sprinkled twice daily and 147 cows were fed the silage alone until calving. The supplement had no effect on the incidence of abortion (1.4 per cent), dystocia (2.3 per cent), fetal maldisposition (7.3 per cent), perinatal mortality (6.0 per cent) or retained fetal membranes (4.0 per cent), but it significantly increased the concentrations of trace elements in the blood and tissues of dead perinatal calves from 10 supplemented dams compared with those from eight unsupplemented dams. It also significantly increased the concentrations of trace elements in the blood of the cows and newborn calves in the supplemented group.