Browsing by Author "Handcock R"

Now showing 1 - 6 of 6
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    Effect of breed and stage of lactation on the solid fat content of milk from cows milked once a day or twice a day
    (Taylor and Francis Group, 2023-11-12) Sanjayaranj I; López-Villalobos N; Blair HT; Janssen PWM; Holroyd SE; MacGibbon AKH; Corner-Thomas R; Handcock R; Sneddon N
    Solid fat content at 10°C (SFC10) is an important parameter of milk fat that influences the spreadability of butter. This study aimed to evaluate the effect of breed and stage of lactation on SFC10 of milk fat from cows milked once a day (OAD) or twice a day (TAD). Milk was collected from 39 Holstein-Friesian (F), 27 Jersey (J), and 34 Holstein-Friesian × Jersey (F × J) cows from a OAD herd and 104 F and 83 F × J cows from a TAD herd in early, mid and late lactation. The SFC10 was predicted using a regression model using milk fatty acid composition. The lower the SFC10, the higher the spreadability of butter. The SFC10 was lower (P < 0.05) for F cows compared with J cows milked OAD. The SFC10 was lower (P < 0.05) for F cows compared with F × J cows milked TAD. The SFC10 was lower in early lactation compared with mid- and late lactation in both milking frequencies. This study revealed that F cow milk and early lactation milk would be suitable for making more easily spreadable butter in OAD and TAD milking. These results could be applicable in the New Zealand dairy industry if consumer preference for more easily spreadable butter increases.
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    Effect of farm system and milk urea phenotype on milk yield and milk composition of dairy cows in Canterbury
    (1/11/2021) Bryant R; O'Conner P; Robic Y; Curtis J; Handcock R; Al-Marashdeh O
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    Heifers with positive genetic merit for fertility traits reach puberty earlier and have a greater pregnancy rate than heifers with negative genetic merit for fertility traits
    (Elsevier Inc on behalf of the American Dairy Science Association, 2021-03) Meier S; McNaughton LR; Handcock R; Amer PR; Beatson PR; Bryant JR; Dodds KG; Spelman R; Roche JR; Burke CR
    This study investigated the hypothesis that dairy heifers divergent in genetic merit for fertility traits differ in the age of puberty and reproductive performance. New Zealand's fertility breeding value (FertBV) is the proportion of a sire's daughters expected to calve in the first 42 d of the seasonal calving period. We used the New Zealand national dairy database to identify and select Holstein-Friesian dams with either positive (POS, +5 FertBV, n = 1,334) or negative FertBV (NEG, -5% FertBV, n = 1,662) for insemination with semen from POS or NEG FertBV sires, respectively. The resulting POS and NEG heifers were predicted to have a difference in average FertBV of 10 percentage points. We enrolled 640 heifer calves (POS, n = 324; NEG, n = 316) at 9 d ± 5.4 d (± standard deviation; SD) for the POS calves and 8 d ± 4.4 d old for the NEG calves. Of these, 275 POS and 248 NEG heifers were DNA parent verified and retained for further study. The average FertBV was +5.0% (SD = 0.74) and -5.1% (SD = 1.36) for POS and NEG groups, respectively. Heifers were reared at 2 successive facilities as follows: (1) calf rearing (enrollment to ∼13 wk of age) and (2) grazier, after 13 wk until 22 mo of age. All heifers wore a collar with an activity sensor to monitor estrus events starting at 8 mo of age, and we collected weekly blood samples when individual heifers reached 190 kg of body weight (BW) to measure plasma progesterone concentrations. Puberty was characterized by plasma progesterone concentrations >1 ng/mL in at least 2 of 3 successive weeks. Date of puberty was defined when the first of these samples was >1 ng/mL. Heifers were seasonally bred for 98 d starting at ∼14 mo of age. Transrectal ultrasound was used to confirm pregnancy and combined with activity data to estimate breeding and pregnancy dates. We measured BW every 2 wk, and body condition and stature at 6, 9, 12, and 15 mo of age. The significant FertBV by day interaction for BW was such that the NEG heifers had increasingly greater BW with age. This difference was mirrored with the significant FertBV by month interaction for average daily gain, with the NEG heifers having a greater average daily gain between 9 and 18 mo of age. There was no difference in heifer stature between the POS and NEG heifers. The POS heifers were younger and lighter at puberty, and were at a lesser mature BW, compared with the NEG heifers. As a result, 94 ± 1.6% of the POS and 82 ± 3.2% of the NEG heifers had reached puberty at the start of breeding. The POS heifers were 20% and 11% more likely to be pregnant after 21 d and 42 d of breeding than NEG heifers (relative risk = 1.20, 95% confidence interval of 1.03-1.34; relative risk = 1.11, 95% confidence interval of 1.01-1.16). Results from this experiment support an association between extremes in genetic merit for fertility base on cow traits and heifer reproduction. Our results indicate that heifer puberty and pregnancy rates are affected by genetic merit for fertility traits, and these may be useful phenotypes for genetic selection.
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    Methane emissions intensity in grazing dairy cows fed graded levels of concentrate pellets
    (Taylor and Francis Group, 2024-05-03) Bosher T; Della Rosa MM; Khan MA; Sneddon N; Donaghy D; Jonker A; Corner-Thomas R; Handcock R; Sneddon N
    The current New Zealand greenhouse gas inventory predictions assume that dairy cows consume pasture only, but the use of supplemental feeds, including concentrates, on New Zealand dairy farms has increased greatly in recent decades. The objective of this study was to evaluate the effect of feeding graded levels of concentrates on methane (CH4) emissions in lactating dairy cows within a pastoral system. Early lactation dairy cows (n = 72) were allocated (n = 18 per treatment) to receive 0, 2, 4 and 6 kg dry matter (DM) of treatment concentrates per day during milking. The cows grazed pasture ad libitum and CH4 emissions were measured in the paddocks using automated emissions monitoring systems called ‘GreenFeed’. Gross CH4 emissions (g/d) were similar for cows across the four dietary treatments, while CH4 emissions intensity (g/kg fat and protein corrected milk production (FPCM) and milk solids production) linearly decreased with increasing concentrate inclusion in the diet (P < 0.02). The CH4 intensity decreased linearly (r2 = 0.42) and quadratically (r2 = 0.53) with increasing FPCM production.
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    Udder and teat morphology traits associated with milk production and somatic cell score in dairy sheep from a New Zealand flock
    (Taylor and Francis Group on behalf of the Royal Society of New Zealand, 2024) Marshall AC; Lopez-Villalobos N; Loveday SM; Weeks M; McNabb W; Handcock R
    The objective of this study was to estimate the phenotypic correlations between udder and teat morphology traits, milk production traits, and somatic cell score in dairy sheep from a flock in New Zealand. A total of 162 lactating ewes were scored for morphology traits during the milk production season of 2021–2022. The 130-d lactation yields of milk, fat, protein, and lactose were obtained with 2–4 test-days from each ewe and modelled using random regression with orthogonal polynomials. Age had a significant effect on all udder and teat traits. Coat-colour (genetic variety within the breed; white or black) was a significant effect for teat angle and udder separation. Udders that were above the hook were associated with lower milk, fat, protein, and lactose yields. Udders with well-defined separation between halves were associated with higher milk, protein, and lactose yields, and with lower somatic cell count. Well-attached udders were associated with lower fat yield and lower somatic cell score. Teats with a backwards angle were associated with lower milk and lactose yields. Further studies are needed to estimate heritability and genetic correlations between these traits to determine whether these traits should be implemented in breeding programs for dairy sheep in New Zealand.