Short communication: Genetic and environmental relationships between milk yield and kidding interval in dairy goats

Abstract

First-parity 305-d milk yield and intervals between first and second kiddings from 1975 through 2005 were analyzed to estimate genetic and environmental parameters for United States Alpine, LaMancha, Nubian, Saanen, and Toggenburg dairy goats. The data set included 43,612 does with first-parity milk yield and 25,863 does with first kidding interval. Parameters were estimated by REML using bivariate mixed models within and across breeds. Fixed effects were month and herd-year of kidding within breed and month and breedherd-year of kidding across breeds. Random effects were animal and residual. The heritability estimate for first-parity milk yield was 0.36 ± 0.01 across breeds and ranged from 0.35 to 0.38 within breed; heritability for first kidding interval was 0.05 ± 0.01 across breeds and ranged from 0.00 to 0.15 within breed. The estimate of the genetic correlation between firstparity milk yield and first kidding interval was positive (unfavorable) across breeds (0.35 ± 0.09). Estimates of environmental correlations within and across breeds were positive (0.16-0.25). The presence of unfavorable genetic relationships between milk yield and kidding interval indicates a need to include reproductive performance as a selection criterion. (Wiggans and Hubbard, 2001), and interval between first and second kiddings were analyzed. Only data from lactations with ≥100 DIM and from herd-year-breed combinations and sires with ≥2 daughter records were retained for final analysis. Records with first kidding intervals of <170 or >730 d were considered to be abnormal and were excluded. Numbers of sires and does for first-parity milk yield and first kidding interval are shown in Table 1 along with means (unadjusted) and phenotypic SD (unadjusted and from the analysis).Data were analyzed within breed (Alpine, LaMancha, Nubian, Saanen, and Toggenburg) with bivariate mixed models that included fixed effects for month and herdyear of kidding. Random effects were animal (with all relationships considered through the inverse of the numerator relationship matrix) and residual. Covariance components were estimated with ASReml (Gilmour et al., 2006). All breeds also were analyzed together by including a breed-herd-year instead of herd-year effect in the model.Heritability estimates for first-parity milk yield (Table 2) were large (0.35-0.38) compared with previous estimates (Montaldo and Manfredi, 2002;

Conformação de úbere de caprinos da raça Saanen: parâmetros estéticos ou funcionais?

“…Além disso, não houve similaridade entre os comportamentos de CMT e CCS. Esses dois testes aferem a CCS da glândula mamária e, portanto, costumam mostrar resultados semelhantes, mesmo sendo o teste do CMT menos sensível (Paape et al, 2007). Assim, acredita-se que esses parâmetros não interferem na celularidade do úbere.…”

“…Vários fatores podem influenciar a CCS, como idade e estado fisiológico do hospedeiro, antecedentes e estágio de infecção, patógeno e fase de lactação (Gomes et al, 2006;Paape et al, 2007;Koop et al, 2010).…”

“…Contudo, a produção de leite também é influenciada por diversos fatores, como tipo de sistema de produção, estágio de lactação, parição, persistência de lactação, número de ordenhas/dia, fatores genéticos, saúde da glândula mamária e nutrição (Montaldo et al, 2010;Tovar-Luna et al, 2010;Goetsch et al, 2011).…”

“…Várias técnicas para detectar a inflamação da glândula mamária têm sido estudadas, sendo as mais aceitas o California Mastitis Test (CMT), pela praticidade a campo, e a Contagem de Células Somáticas (CCS), em razão de sua sensibilidade e especificidade (Paape et al, 2007;Mira et al, 2013).…”

Trends in goat research, a review

“…The same research group investigated the effect of continuous lactation on mammary remodelling during the late gestation and lactation, reporting that the continuously lactating gland resembled a normally lactating gland in an advanced stage of lactation (Safayi et al 2010b). The relationship (genetic and environmental) between milk yield and kidding interval was investigated by Montaldo et al (2010), who summarised that the presence of unfavourable genetic relationships between milk yield and kidding interval indicates a need to include reproductive performance as a selection criterion in dairy goats.…”