Animal growth is a complex and dynamic process that involves physiological and morphological changes from hatching to maturity. It is defined as the increase in body size per time unit. Mathematical functions, called growth models, have been used to explain growth patterns. The aim of this study was to compare the Gompertz-Laird, logistic, Richards, and Von Bertalanffy growth models to determine which best fits the data of the Creole chickens ( CC ). Three hundred forty-seven CC were individually weighed from hatching until 177 D of age. Birds were fed a starter diet (0–18 D of age; 19% crude protein ( CP ) and 3,000 kcal of ME/kg) and grower diet (19–177 D of age; 18% CP and 2,800 kcal of ME/kg). Data were analyzed using PROC NLIN to fit the nonlinear growth curve. The coefficient of determination ( R 2 ), Akaike information criteria ( AIC ), and Bayesian information criteria ( BIC ) were used to compare the goodness of fit of the models. The Von Bertalanffy (R 2 : 0.9382, 0.9415; AIC: 2,224.1, 2,424.8; BIC: 2,233.5, 2,434.3, for females and males, respectively) was the model that best explained growth of the birds. On the other hand, both the Gompertz-Laird and logistic models overestimated hatching BW and underestimated the final BW of CC. Females reached age of maximum growth faster than males. The asymptotic weight was higher in males (3,011 g) than in females (2,011 g). Body weight at inflection point was 892 g at 64 D of age for males and 596 g at 54 D for females. In conclusion, the best fit of the data was obtained with the Von Bertalanffy growth model; the information is intended to serve as the basis for utilizing CC.

Heritabilities and correlations for milk yield (MY), fat yield (FY), protein yield (PY), combined fat and protein yield (FPY), fat percentage (F%), protein percentage (P%), age at first kidding (AFK), interval between the first and second kidding (KI), and real and functional productive life at 72mo (FPL72) of 33,725 US dairy goats, were estimated using animal models. Productive life was defined as the total days in production until 72mo of age (PL72) for goats having the opportunity to express the trait. Functional productive life was obtained by correcting PL72 for MY, FY, PY, and final type score (FS). Six selection indexes were used, including or excluding PL72, with 6 groups of different economic weights, to estimate the responses to selection considering MY, FY, PY, and PL72 as selection criteria. The main criteria that determined the culling of a goat from the herd were low FS, MY, and FY per lactation. Heritability estimates were 0.22, 0.17, 0.37, 0.37, 0.38, 0.39, 0.54, 0.64, 0.09, and 0.16 for PL72, FPL72, MY, FY, PY, FPY, F%, P%, KI, and AFK, respectively. Most genetic correlations between the evaluated traits and PL72 or FPL72 were positive, except for F% (-0.04 and -0.06, respectively), P% (-0.002 and -0.03, respectively), and AFK (-0.03 and -0.01, respectively). The highest genetic correlations were between FPL72 and MY (0.39) and between PL72 and MY (0.33). Most phenotypic correlations between the traits evaluated and FPL72 and PL72 were positive (>0.23 and >0.26, respectively), except for F% (-0.004 and -0.02, respectively), P% (-0.05 and -0.02), KI (-0.01 and -0.07), and AFK (-0.08 and -0.08). The direct selection for PL72 increased it by 102.28d per generation. The use of MY, FY, PY, KI, or AFK as selection criteria increased PL72 by 39.21, 27.33, 35.90, -8.28, or 2.77d per generation, respectively. The inclusion of PL72 as selection criterion increased the expected response per generation from 0.15 to 17.35% in all selection indices studied.

Thesis typed by Georgette Fosque for GLAFIRO TORRES-HERNANDEZ 2 respect to repeated observations on the same ewe. The correlation between subjective condition score and total milk production was -.25.

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Uso de un alimento integral como complemento a cabras locales en pastoreo:respuesta en producción y composición química de la leche Use of total mixed ration as supplement in grazing local goats: Milk production response and chemical composition ResumenEn México, la población caprina se concentra en sistemas de producción extensivos, con hatos formados en mayoría por cabras que los productores llaman criollas, denominación ahora aceptada como locales. La alimentación de la cabra lechera en el sistema extensivo es a través del pastoreo, pero éste, por sí solo no puede satisfacer las necesidades nutricionales de la cabra. Por tanto, si se quiere aumentar la producción de leche, es necesario complementar la alimentación de las cabras en pastoreo. Al respecto, en rumiantes en pastoreo que han sido complementados con un alimento integral se han reportado aumentos en la producción de leche. Por lo tanto, el objetivo de estudio fue evaluar el efecto en la producción y composición de la leche de cabras locales en pastoreo complementadas con un alimento integral. Para ello, se realizaron dos experimentos. En el primero, se evaluó el efecto de cambiar de un sistema de pastoreo a uno estabulado, con el fin de desafiar a las cabras a que expresaran su potencial productivo al ofrecerles un alimento integral. En el segundo, se evaluó el efecto en producción de leche y componentes de la leche de cabras en pastoreo al complementarlas con diferentes niveles del alimento integral usado en el experimento 1. Los datos de producción de leche y composición química en leche de ambos experimentos fueron analizados utilizando un modelo de medidas repetidas. Los datos de peso vivo y condición corporal final de las cabras, se analizaron como un diseño completamente al azar. Se realizó un análisis de costos parciales en ambos experimentos, con el fin de conocer la viabilidad económica de los tratamientos. En el experimento 1, la concentración de grasa en leche no se modificó (p > 0.05) por efecto de tratamientos, pero si AbstractIn Mexico, the goat population is concentrated in extensive production systems in Mexico, with herds mainly formed by goats that the producers called Creoles, now accepted as a local name.The power of the goat dairy in the extensive production system, is through the grazing, but this alone cannot meet the nutritional needs of the goat. Therefore, if the producers want to increase the production of milk, it is necessary to supplement the grazing goat diet with grains. On this manner, some results report an increase in milk production in grazing ruminants supplemented with an integral diet. The aim of this study was to evaluate the effect on the production and composition of milk in grazing local goats supplemented with an integral feed. Two experiments were performed. The first, evaluated the effect of changing from a grazing system to intensive system, in order to challenge the goats to express their productive potential by providing them with an integral feed. In the second, it evaluated the effect in grazing lo...

Two groups of six Haemonchus contortus infected Saint Croix lambs each received different diets for 11 weeks: control group, commercial food, molasses and lucerne hay; and treated group, nutritional pellets (NPs) containing Duddingtonia flagrans at 2 × 106 chlamydospores/kg body weight (BW), sorghum and lucerne hay. Mean BW gain (BWG), body condition score (BCS) and packed cell volume (PCV) and also eggs/g of faeces (EPG) and recovered L3 were compared using a repeated measures across time model. Groups had similar BWG (control 139.7 ± 0.035 g/day and treated 167.7 ± 0.041 g/day), BCS (control 3.6 ± 0.39 and treated 3.4 ± 0.46) and PCV (control 32.5 ± 1.68% and treated 30.0 ± 1.68%). The mean EPG of the control group was 1215 ± 1040 and in the treated group it was 2097.91 ± 2050. No reduction in larval population was observed during weeks 2 and 3. The greatest larval population reduction in the faeces of treated lambs was observed during the first week (70.5%) and from weeks 6 to 11, with a mean value close to 70% (P < 0.05). In general, both experimental groups showed a similar feed conversion. It was concluded that both diets resulted in similar lamb growth, PCV, BCS and H. contortus EPG. However, NP consumption significantly reduced the H. contortus L3 population in lamb faeces.