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Item Should lambs born to one-year-old ewes and grown to heavy live weights be retained as replacements and mated at seven months of age?(Taylor & Francis Group, 2024-02-21) Haslin E; Kenyon PR; Corner-Thomas RA; Morris ST; Blair HTThe lifetime productivity and efficiency of singleton- and twin-born ewe lambs born to one-year-old ewes were compared with twin-born ewe lambs born to mixed-age ewes. Romney ewe lambs either born as twins to mixed-age ewes (Heavier n = 135 and Control n = 135), or to one-year-old ewes as singletons (L1; n = 135) or twins (L2; n = 88) were included. The Heavier ewes weighed 47.9 ± 0.36 kg at ewe lamb breeding while Control ewes weighed 44.9 ± 0.38 kg. The lifetime number of lambs born and weaned, and the lifetime weight of lambs weaned were used to calculate both feed and ewe efficiency. Heavier ewes had greater lamb production as one-year-old ewes than L1, L2 and Control ewes, after which the yearly lamb production and efficiency did not differ between treatments. Heavier ewes had a greater lifetime number and weight of lambs weaned than L1 and L2 ewes but did not differ from Control ewes. The lower lifetime production of L1 and L2 ewes was driven by their low production as one-year-old ewes. Farmers, therefore, could select their replacements from ewes born to one-year-old ewes and have similar lamb production to ewes born to mixed-age ewes, providing they reach recommended pre-breeding live weights.Item Development of an assay for the determination of dietary apparent ileal nitrogen and amino acid digestibilities in the meat chicken : a thesis presented in partial fulfilment of the requirements for the degree of Master of Agricultural Science in Animal Science at Massey University(Massey University, 1991) Yap, Kee HorBiological procedures which quantify protein value are expected to beneficially influence efficiency of nutrient provision in dietary formulations for the livestock, industry. This thesis provides a review of two widely employed quantitative assessments, "Digestibility" and "Availability" and in the experimental section describes a series of experiments undertaken on meat chicken to refine assay procedures involved in the determination of protein and amino acid apparent ileal digestibility values. Five experiments were undertaken. (1a) A comparison of two feeding procedures with three diets differing in particle size with a view to evaluating the effect of feeding behaviour on the final composition of the test diet in the crop. (1b) Determination of crop residue composition associated with time following feeding with two feeding procedures and two diets differing in particle size. (2) A comparison of the effects of two slaughter procedures and two flushing solutions on ileal N digestibility of meat and bone meal. (3) A comparison of the effect of time of slaughter following feeding on ileal N values of two diets. (4) Determination of the effect of length of ileum on ileal N digestibility values of two diets. (5) Determination of the effect of age on ileal N and AA digestibilities of two diets. In 1a there was clear evidence that bird eating behaviour and particle size of the test diet influenced crop content proportions of a number of criteria, more notably chromium and nitrogen. For coarse particle diets an intubation feeding procedure produced a closer match of material in the crop with that of the untouched diet than a free access provision of food procedure. In 1b the results of the study were inconclusive and no satisfactory cause for inconsistencies that developed between treatments could be found. In 2, two slaughter procedures, euthanasia by sodium pentobarbitone and asphyxiation by carbon dioxide, resulted in significantly different (P<0.05) apparent ileal nitrogen (N) digestibility. Differences between flushing solutions, distilled water and physiological saline were small and not significant (P<0.05). In 3, for two diet types, N and dry matter (DM) digestibilities were relatively constant over sampling times of 2 to 5 hours following the start of feeding. Ileal digesta sampled quantities tended to be greatest at the 4 hour sampling interval. In 4, differences in N and DM digestibilities of digesta samples drawn from sections of the ileum up to 30 cm in length as measured from the ileo-caecal junction were generally small and non significant. In 5, bird age had no significant effect on N and DM digestibilities. The main conclusions drawn were that intubation better retained the integrity of food reaching the crop. Sodium pentobarbitone was a preferable method of slaughter. Ileal length sampled needed to be kept as short as consistant with providing adequate sample material and largest sample sizes were obtainable around 4 hours following the start of feeding.Item Comparison of milking characteristics and feed conversion efficiency of two lines of Holstein-Friesian cows which differ genetically in live weight : a thesis presented in partial fulfilment of the requirements for the degree of Master of Applied Science in Dairy Production at Massey University, Palmerston North, New Zealand(Massey University, 2002) Tolosa Alvarez, Maria XimenaMilking characteristics during peak yield in two consecutive lactations (seasons 2000 and 2001, experiment one); daily milk production and composition, somatic cell count, live weight and body condition score during a complete lactation (2000 season, experiment two); and metabolisable energy intake and feed conversion efficiency during peak lactation (1999 season, experiment three) were studied in three experiments with grazing Holstein-Friesian cows from two selection lines, which differed genetically for live weight. Experiment one (a & b): the heavy line yielded more milk at each milking than the light line but this difference was not significant for any season. Average flow rates were similar for both lines in both lactations (~2.0 litres/min for both lines). Maximum flow rates did not differ between lines either (~3.2 litres/min for both lines). Consequently, total milking times were similar for both lines in both lactations (7.5 vs. 7.3 min and 7.6 vs. 7.8 min for the heavy and the light line for seasons 2000 and 2001 respectively). Experiment two: Cows from the heavy and the light line yielded 22.2 and 20.6 litres/day respectively (p<0.01). Fat yield was similar for both lines because the milk from the light cows had a higher fat concentration than milk from the heavy (4.8 vs. 5.0%; p<0.05). The heavy line yielded more milk protein than the light line (0.8 vs. 0.7 kg/day; p<0.05), however, there were no significant differences between lines for protein concentration. Log transformed milk somatic cell counts were slightly lower for the heavy line both in peak lactation and during the whole lactation, however, this difference was significant only during peak lactation in 2001 (10.8 vs. 11.4x103 cells/ml of milk, p<0.001; and 10.3 vs. 10.8x103 cells/ml of milk, p<0.05 for the heavy and light line for period one and two respectively). Differences in live weight between the heavy and the light line were significant (517 vs. 474 kg for the heavy and the light line respectively; p<0.001). Body condition score during the whole lactation was similar for both lines (4.2). Experiment three: metabolisable energy intake and feed conversion efficiency in peak lactation were similar for both lines (158 vs. 161 MJ ME/cow/day and 108 vs. 106 g MS/kg DM intake for the heavy and the light line respectively). The regression coefficient of metabolisable energy intake on metabolic live weight was 0.65 MJME/kg LW0.75 for both lines. In summary, selection for cow live weight affected the live weight of the cows, had no effect on milk production, and in contrast with other experiments, had no effect on individual pasture intake either per cow or per kg of metabolic live weight nor on energy requirements for maintenance. Finally, selection for cow live weight did not have a consistent effect on milking characteristics or milk somatic cell counts.