G. A. Wickham

Effects of pre‐lamb shearing on feed intake and associated productivity of May‐ and August‐lambing ewes

Abstract The effects of pre‐lamb shearing on feed intake and wool/lamb production of May (autumn)‐ and August (spring)‐lambing ewes were examined. Mixed age Border Leicester x Romney ewes mated to lamb in May or August (60 ewes/ lambing policy) were divided at random into two groups (balanced for pregnancy status and liveweight). One group was shorn on Day 118 of pregnancy (P118) and the second group left unshorn. Measurement of pasture intake was carried out over three periods before lambing (P113–117, P119–130, and P141–144) and three periods after lambing (L (lactation day) 8–11, L21–25, and L29–33) using intraruminal chromic oxide controlled release capsules. Intake of ewes was not affected by shearing treatment during pregnancy or lactation except during P141–144 when organic matter intake was significantly greater for shorn ewes than for unshorn ewes (1739 ±58 versus 1526 ± 59 g/day, P < 0.05). Ewe liveweights and condition scores were similar for both shearing treatments during pregnancy and lactat...

Selection responses in New Zealand Romney sheep: 2. Selection for yearling greasy fleece weight

Data from a flock selected for high yearling greasy fleece weight and a randomly selected control group, derived from the same base flock, were analysed. Each flock contained 70-80 mixed-age breeding ewes mated to 4 rams each year. Data from yearlings born in the flocks from 1956 to 1979 were analysed. On average, they represented 8.5 generations. The accumulated selection differential in the selection flock was about 5 kg, and this resulted in a genetic response to selection of 0.7-0.8 kg in yearling greasy fleece weight. Estimates of the realised heritability of greasy fleece weight ranged from O. 10 to 0.17. Several significant correlated responses occurred in the yearling data. Relative to control flock means: clean fleece weight, staple length, mean fibre diameter, clean scoured yield, weaning weight, and liveweight increased; whereas quality number and crimp frequency decreased. Mean date-of-birth became earlier. Lifetime averages of the performance of ewes born between 1956 and 1971 indica...

Selection response in New Zealand Romney sheep

Abstract Data from a flock selected for wool-free faces, and a random-selected control group derived from the same base flock were analysed. Each flock consisted of 70–80 breeding ewes, mated usually to 4 rams each year. Estimates of the realised heritability of face-cover grade ranged from 0.44 to 0.68. Correlated responses derived from yearling data were generally negligible. Relative to control group means: liveweight, staple length, and fibre fineness increased slightly in both the yearling ewes and rams; clean scoured yield and fibre uniformity increased in the yearling ewes; and fleece weights were slightly lower in both sexes. Data on the lifetime averages of ewes born between 1956 and 1971 indicated that, relative to the control group, staple length and fibre fineness showed small increases.

Analysis of records of a Perendale flock

Abstract Genetic parameters for weaning and yearling (14-15 months) traits were estimated using 3313 half-sib records from 62 sires and 1720 daughter-dam pairs. The estimates of heritability by paternal half-sib and daughter-dam regression analyses were respectively: weaning weight (WW) 0.20 and 0.16, hogget body weight (BW) 0.27 and 0.44, greasy fleece weight (FW) 0.32 and 0.30, quality number (ON) 0.26 and 0.13, fibre diameter (FD) 0.54 and 0.47, staple length (SL) 0.49 and 0.35, and fleece character (FC) 0.23 and 0.23. Estimates of genetic correlations were in the following ranges: Medium negative (−0.4 to −0.6) BW × FC, ON × SL; Low negative (−0.2 to −0.4) WW × ON, FD × FC, ON × FW, ON × FD; Low positive (0.2 to 0.4) BW × WW, BW × ON, SL × FC; Medium positive (0.4 to 0.6) FW × FD, FW × FC; High positive (0.6 and over) FW × SL. Phenotypic correlations generally agreed with the genetic correlations. Important exceptions were BW × FW and BW × FD. Among the environmental factors studied, age-of-dam and re...

Intravenous infusion of cysteine and wool growth of romney sheep

Abstract New Zealand Romney wethers were infused intravenously with 2 and 4 g per day of cysteine hydrochloride. Their wool growth rates were compared with those of saline-infused controls. Cysteine infusion apparently counteracted the winter depression in wool growth. No difference in response between 2 and 4 g per day was detected. In a second experiment, New Zealand Romney wethers were fed two dietary protein levels and were infused with 2 g per day of cysteine hydrochloride. Their wool growth rates were compared with saline-infused controls fed comparable levels of dietary protein. Significant increases (p < .01) in wool growth rate from the cysteine-infused sheep and a significant protein level × cysteine infusion interaction were observed. The sheep fed the high-protein diet grew more wool than those fed the low-protein diet.

Analysis of records of a Perendale flock V. Repeatabilities and genetic correlations between ages

Abstract Repeatabilities of greasy fleece weight (FW), staple length (SL), mean fibre diameter (FD), quality number (QN), fleece character (FC), and number of Iambs weaned (NL W) were calculated by regressing older records on younger records in data collected from a flock of Perendale ewes. Average repeat abilities of the wool traits were: FW, 0.62|SL, 0.50|FD, 0.71|QN, 0.46|and FC, 0.18. The repeatabilities of the various components of NL W were low. Genetic correlations between records of each trait collected at different ages were also calculated. With quality number, fleece character, and fleece weight there were indications of genotype x age interactions. A low genetic correlation between hogget and lifetime average fleece weight, coupled with earlier estimates of lower heritability of fleece weights in hoggets, suggests that selection on hogget fleece weight is considerably less effective than selection on 2-year-old fleece weight in terms of lifetime average response.

Analysis of records of a Perendale flock IV. Estimates of genetic and phenotypic parameters for mature ewes

Abstract Heritability and genetic and phenotypic correlation estimates were derived from data on 2-yearold (n = 1724), 3-year-old (n = 1160), 4-year-old (n = 726), and 5-year-old (n = 449) ewes. The traits studied were greasy fleece weight (FW), staple length (SL), mean fibre diameter (FD), quality number (QN), fleece character (FC), and number of lambs weaned (NL W). Pooled averages of the heritabilities, derived by weighting the paternal half-sib (PHS) estimates and 2-, 3-, and 4-year daughter-dam (DDR) estimates according to their standard errors were: FW, 0.47; SL, 0.40; FD, 0.50; QN, 0.35; FC, 0.24; NLW, 0.07; fertility, 0.01; and twinning, 0.09. The estimates of the genetic correlation between FW and NL W averaged around the negligible to low negative range. The phenotypic correlations were similar in sign and magnitude to the genetic correlation.

Weaning weight adjustments for selecting lambs born to year-old ewes

Abstract Data from the New Zealand sheep recording scheme (Sheeplan) were analysed to derive estimates of factors affecting weaning weights of lambs from l-year-old dams, and to compare these with estimates from lambs reared by older dams. The linear regression of weaning weight on age at weaning was higher for progeny of yearling ewes than those of older ewes. This probably resulted from later lambing and younger weaning of lambs from yearling ewes. Birth/rearing rank and sex effects were similar for progeny of yearling and older ewes. There was considerable variation between flocks in the size of the effect ascribed to yearling dams. This probably reflects differences in management between yearling dams and older dams in the flocks analysed.

A comparison of wool follicle development of New Zealand Romney lambs at two stocking levels

Abstract The follicle populations of lambs born to two groups of Romney ewes grazed at different stocking rates were studied. The low stocking level was 5 ewe equivalents per acre, and the high level approximately double the low level. In 1966, 69 ewe lambs were sampled at approximately 13 and 56 weeks of age. In 1967, 24 mixed-sex lambs were sampled at birth and approximately 13 weeks of age. Though the lambs from the older ewes grew raster in 1966, there were no effects shown by the follicle population. There was a difference between years in the rate of attaining the maximum Sf/Pf value. Despite variation in body growth, the retardation in secondary follicle maturation which was observed was only transient, and there was no permanent effect of stocking rate or twin birth on Sf/Pf ratio. Follicle densities differed between stocking levels, but only as a result of differences in skin stretching due to body size.

Wool growth and plasma amino acid responses of N.Z. romney sheep to formalin-treated casein and methionine supplements

Abstract Lactic casein was treated with formalin in an attempt to protect the protein against ruminal degradation. Sheep received diets supplemented with 100 g/day of treated casein. Wool growth and the level of free amino acids in the plasma were compared with those of sheep receiving no supplement or untreated casein. A fourth group of sheep received a supplement of 1 g/day of methionine hydroxy analogue (MHA) mixed with 5 g of casein, the mixture being formalin treated after blending. Substantial wool growth increases from midside areas resulted from both the formalin-treated and the untreated casein supplements. Significant differences occurred in the levels of free citrulline, valine, leucine, histidine, proline, and ɛ-N-methyl lysine in the plasma. With each of these amino acids the untreated-casein supplemented sheep showed a small increase and the treated-casein group a larger increase when compared with the control group. No change in either wool growth or free amino acids resulted from the MHA s...