Environmental Sensitivity in New Zealand Dairy Cattle

Abstract

This study quantifies the extent of within-breed sire reranking for milk production traits in a range of environments encountered within New Zealand. Character states of herds were formed within the environmental ranges of herd fat plus protein (MS) yield, summer heat load index (HLI), herd size, and altitude. Single-trait and bivariate sire models across breeds were then applied for estimation of genetic parameters and genetic correlations between extreme character states. A low degree of sire reranking occurred, as measured by genetic correlations around 0.9, between herd environments that differed widely in MS yield (227 vs. 376 kg of MS per cow), and HLI (61.4 vs. 69.6). The HLI of 61.4 and 69.6 are approximately equivalent to average summer maximum temperatures of 19 and 25 degrees C at 80% humidity. Correlations of sire estimated breeding values in extreme character states were low, but only one was below an expected correlation accounting for the reliability of prediction. The results show the environment in New Zealand is not sufficiently diverse to warrant separate breeding schemes for different environments.

Seasonal variations in the composition of Holstein cow’s milk and temperature–humidity index relationship

“…The genetic improvement in milk yield experienced over the last few decades is often in conflict with maintaining homeothermy . This supports the evidence reported by Bryant et al (2007): cows with high genetic merit were more susceptible to the effects of hot environments than their low genetic merit counterparts. Finally, in the American study, each test-day record was assigned to daily weather records, whereas the THI values used in this study were recorded 2 days before the sampling day.…”

“…Conversely, still less information is available regarding the relationship between THI and milk fat and protein percentage. In a New Zealand study, Bryant et al (2007) reported patterns for fat and protein with a drop that occurred around the values of 50 and 60 THI, respectively. These results support the findings of this study insofar as they indicate the high sensibility of fat and protein to hot conditions.…”

“…These results support the findings of this study insofar as they indicate the high sensibility of fat and protein to hot conditions. One should recall that the Bryant et al (2007) study referred to different field conditions than the ones of this study, mainly because of the farming systems adopted. In particular, in the New Zealand study, the dairy cows were raised under a grazing system, whereas in this study the dairy cows were confined within free stall housing with no time at pasture.…”

Effect of Holstein–Friesian genetic group on peripartum and early lactation haematological and acute phase proteins profiles, health and fertility

“…In North America where cows are predominantly kept indoors on total mixed rations (i.e. confinement), a different set of breeding goals has been derived compared to NZ where cows are outdoors all year round on grass (Boettcher et al, 2003;Bryant et al, 2007). Cows of NA ancestry have high milk output achieved with maximal energy inputs and have traditionally been aggressively selected for milk yield, increased body size and some phenotypic traits such as udder conformation.…”

The use of temperature-humidity index (thi) to evaluate temperature-humidity conditions in freestall barns

“…The negative impact of heat stress on productivity and reproductive performance of dairy cattle and the associated economic consequences have been well documented (Fuquay, 1981;Omiński et al, 2002;Ravagnolo and Misztal, 2002;de la Casa and Ravelo, 2003;St-Pierre et al, 2003;Bryant et al, 2007;Jordan, 2003;Garcia-lspierto et al, 2007). However, most of this research has focused on hot regions while paying little attention to temperate zone countries such as Poland (Jaśkowski et al, 2005;Głuski and Michalczyk, 2008).…”