Browsing by Author "Blair H"
Now showing 1 - 4 of 4
Results Per Page
Sort Options
- ItemLow Birthweight Beef Bulls Compared with Jersey Bulls Do Not Impact First Lactation and Rebreeding of First-Calving Dairy Heifers—A Case Study in New Zealand(MDPI (Basel, Switzerland), 2022-03) Coleman L; Martín N; Back P; Blair H; López-Villalobos N; Hickson R; Bittante G; Mantovani RDairy heifers in New Zealand are typically naturally mated by Jersey bulls to produce low-value non-replacement offspring sold for slaughter a few days after birth. Producing a beef-sired calf from a dairy heifer will increase the value of these calves for beef production but may compromise the subsequent career of the animals, in terms of milk production, rebreeding success, health, or survival of the heifer. This study aimed to determine the impact of low birthweight Angus and Hereford bulls versus breed-average Jersey bulls on the reproduction and production traits of first-calving dairy heifers. The experiment included 304 heifer-calf pairs over 2 years. Calves sired by Angus and Hereford bulls were 3.5–4.4 kg and 3.7–6.8 kg heavier than Jersey-sired calves and had a 4.2% and 9.3% incidence of assistance at birth for normally presented calves over the 2 years, respectively. No normally presented Jersey-sired calves were assisted. There was no difference in body condition score, pre-calving live weight, milk production, pregnancy rate, inter-calving interval, re-calving day, and 21-day re-calving rate of heifers mated to the different breeds of bulls. The results indicate that the Angus and Hereford bulls with low birthweight and high direct calving ease estimated breeding values (EBV) can be used to produce calves of greater value than Jersey-sired calves without impacting dairy heifer production. However, a small increase in assistance at calving could be expected.
- ItemService Sire Effects on Body Condition Score, Milk Production, and Rebreeding of Mixed-Aged Dairy Cows Bred to Angus and Hereford Bulls—A Case Study in New Zealand(MDPI (Basel, Switzerland), 2021-12-01) Coleman L; Back P; Blair H; López-Villalobos N; Hickson R; Meyer UBeef-breed bulls are used in dairy herds to produce a calf of greater value for finishing than calves sired by dairy bulls. There is limited research about which beef-breed bulls are most appropriate, and whether any negative impact on cow performance in terms of milk production and rebreeding should be considered. The aim of this case study was to compare the body condition score, milk production, and rebreeding performance of mixed-aged dairy cows bred to a selection of Angus and Hereford beef-breed bulls. Body condition score, post-calving live weight, milk production, rebreeding performance, and survival of 952 mixed-aged dairy cows artificially bred to 65 Angus and Hereford bulls were compared. There was no effect of service sire on post-calving live weight, days in milk, milk production, or inter-calving intervals of mixed-aged cows. Service sire had an effect on the calving day due to differences in gestation length (p < 0.001), although this did not translate into an effect on days in milk. A longer gestation length negatively influenced pregnancy rates, and greater birth weight of the calf negatively influenced survival to rebreeding (p < 0.05), indicating the potential for an effect of service sire. Selection of beef-breed service sires for dairy cows should include emphasis on lighter calves and shorter gestation lengths. The general absence of the service sire effect on the parameters measured in this study indicated that any of the service sires used in this experiment would be appropriate for use over dairy cows.
- ItemSire Effects on Birth Weight, Gestation Length, and Pre-Weaning Growth of Beef-Cross-Dairy Calves: A Case Study in New Zealand(MDPI (Basel, Switzerland), 2021-09-01) Coleman L; Back P; Blair H; López-Villalobos N; Hickson R; Meyer UProduction of beef-cross-dairy calves from dairy cows increases the value of non-replacement calves born to the dairy herd. The use of beef-breed sires may impact on calf birth weight, gestation length and pre-weaning growth rate of calves, which in turn influences the profitability of the dairy farm. The aim of this case study was to compare the birth weight, gestation length, and pre-weaning growth of progeny born to mixed-aged dairy cows on a single farm which were artificially bred to a selection of Angus and Hereford bulls, typical of those used over dairy herds in New Zealand. The birth weight, gestation length and pre-weaning growth of 980 calves sired by 65 sires were compared. Mean progeny birth weight (range 33.3–41.4 kg), gestation length (range 276.1–288.6 days), age at weaning (range 70.3–88.3 days) and pre-weaning ADG (range 0.63–0.76 kg/d) differed among sires (p < 0.001). There was a negative genetic correlation (−0.31) and positive phenotypic correlation (0.36) between gestation length and birth weight. Age at weaning was negatively correlated with birth weight (genetic: −0.56, phenotypic: −0.57). Bulls used in this study, and other bulls with similar genetic merit for birth weight and gestation length would be suitable for mating mixed-aged dairy cows in New Zealand.
- ItemThe Effect of Age of Dam and Birth Rank on the Reproductive Performance of Ewes as One- and Two-Year-Olds.(2021-03-10) Pettigrew E; Hickson R; Morris S; Kenyon P; Corner-Thomas R; Haslin E; Blair HCurrently, 30-43% of New Zealand sheep farmers breed their ewe lambs, but few retain the offspring as replacements for their flock. No difference in lamb production as a yearling among singletons and twins born to ewe lambs and twins born to mature ewes has been reported, provided the ewe lambs had reached the 60-65% of their likely mature weight prior to breeding at seven to eight months of age. The aim of this experiment was to determine the lamb production from singletons and twins born to ewe lambs and twins born to mature ewes during their first two years of lambing. The experiment included 8-month-old ewes born as twins to mature ewes (M2, n = 135), singletons born to ewe lambs (L1, n = 135), and twins born to ewe lambs (L2, n = 88), bred during the same period to the same rams, over two years. The efficiency of lamb production (total litter weight at weaning divided by the pre-breeding weight of the ewe, for all ewes presented for breeding) after two years of production was not significantly different (p > 0.05) among the groups (0.40 ± 0.02, 0.39 ± 0.02, and 0.39 ± 0.03, for M2, L1, and L2, respectively).